toolchain-utils: migrate all in-use projects to python 3

This patch migrates all in-use projects left to python 3.

BUG=chromium:1011676
TEST=Passed unittests and launched scripts manually.

Change-Id: I7f2de4e1131c05bacfac80667f3064da8adaebfd
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/2051397
Reviewed-by: George Burgess <gbiv@chromium.org>
Tested-by: Zhizhou Yang <zhizhouy@google.com>
Auto-Submit: Zhizhou Yang <zhizhouy@google.com>

29 files changed, 498 insertions, 414 deletions

diff --git a/afdo_redaction/redact_profile.py b/afdo_redaction/redact_profile.py
index 96375fee..02bae928 100755
--- a/afdo_redaction/redact_profile.py
+++ b/afdo_redaction/redact_profile.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright 2018 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -30,6 +30,7 @@ import collections
 import re
 import sys
 
+
 def _count_samples(samples):
   """Count the total number of samples in a function."""
   line_re = re.compile(r'^(\s*)\d+(?:\.\d+)?: (\d+)\s*$')
@@ -132,7 +133,7 @@ def _read_textual_afdo_profile(stream):
       continue
 
     if line[0].isspace():
-      assert function_line is not None, "sample exists outside of a function?"
+      assert function_line is not None, 'sample exists outside of a function?'
       samples.append(line)
       continue
 
@@ -170,12 +171,13 @@ def dedup_records(profile_records, summary_file, max_repeats=100):
     counts[_normalize_samples(record.samples)].append(record)
 
   # Be sure that we didn't see any duplicate functions, since that's bad...
-  total_functions_recorded = sum(len(records)
-                                 for records in counts.itervalues())
+  total_functions_recorded = sum(len(records) for records in counts.values())
 
-  unique_function_names = set(record.function_line.split(':')[0]
-                              for records in counts.itervalues()
-                              for record in records)
+  unique_function_names = {
+      record.function_line.split(':')[0]
+      for records in counts.values()
+      for record in records
+  }
 
   assert len(unique_function_names) == total_functions_recorded, \
       'duplicate function names?'
@@ -187,7 +189,7 @@ def dedup_records(profile_records, summary_file, max_repeats=100):
   num_samples_total = 0
   num_top_samples_total = 0
 
-  for normalized_samples, records in counts.iteritems():
+  for normalized_samples, records in counts.items():
     top_sample_count, all_sample_count = _count_samples(normalized_samples)
     top_sample_count *= len(records)
     all_sample_count *= len(records)
@@ -205,11 +207,13 @@ def dedup_records(profile_records, summary_file, max_repeats=100):
     for record in records:
       yield record
 
-  print('Retained {:,}/{:,} functions'.format(num_kept, num_total),
-        file=summary_file)
-  print('Retained {:,}/{:,} samples, total'.format(num_samples_kept,
-                                                   num_samples_total),
-        file=summary_file)
+  print(
+      'Retained {:,}/{:,} functions'.format(num_kept, num_total),
+      file=summary_file)
+  print(
+      'Retained {:,}/{:,} samples, total'.format(num_samples_kept,
+                                                 num_samples_total),
+      file=summary_file)
   print('Retained {:,}/{:,} top-level samples' \
             .format(num_top_samples_kept, num_top_samples_total),
         file=summary_file)
@@ -220,15 +224,17 @@ def run(profile_input_file, summary_output_file, profile_output_file):
 
   # Sort this so we get deterministic output. AFDO doesn't care what order it's
   # in.
-  deduped = sorted(dedup_records(profile_records, summary_output_file),
-                   key=lambda r: r.function_line)
+  deduped = sorted(
+      dedup_records(profile_records, summary_output_file),
+      key=lambda r: r.function_line)
   for function_line, samples in deduped:
     print(function_line, file=profile_output_file)
     print('\n'.join(samples), file=profile_output_file)
 
 
 def _main():
-  run(profile_input_file=sys.stdin, summary_output_file=sys.stderr,
+  run(profile_input_file=sys.stdin,
+      summary_output_file=sys.stderr,
       profile_output_file=sys.stdout)
 
 
diff --git a/afdo_redaction/redact_profile_test.py b/afdo_redaction/redact_profile_test.py
index 27fb534e..e2438972 100755
--- a/afdo_redaction/redact_profile_test.py
+++ b/afdo_redaction/redact_profile_test.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright 2018 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -8,12 +8,12 @@
 
 from __future__ import division, print_function
 
-import StringIO
+import io
 import unittest
 
-import redact_profile
+from afdo_redaction import redact_profile
 
-_redact_limit = redact_profile.dedup_records.func_defaults[0]
+_redact_limit = redact_profile.dedup_records.__defaults__[0]
 
 
 def _redact(input_lines, summary_to=None):
@@ -21,17 +21,18 @@ def _redact(input_lines, summary_to=None):
     input_lines = input_lines.splitlines()
 
   if summary_to is None:
-    summary_to = StringIO.StringIO()
+    summary_to = io.StringIO()
 
-  output_to = StringIO.StringIO()
-  redact_profile.run(profile_input_file=input_lines,
-                     summary_output_file=summary_to,
-                     profile_output_file=output_to)
+  output_to = io.StringIO()
+  redact_profile.run(
+      profile_input_file=input_lines,
+      summary_output_file=summary_to,
+      profile_output_file=output_to)
   return output_to.getvalue()
 
 
 def _redact_with_summary(input_lines):
-  summary = StringIO.StringIO()
+  summary = io.StringIO()
   result = _redact(input_lines, summary_to=summary)
   return result, summary.getvalue()
 
@@ -64,6 +65,7 @@ def _generate_repeated_function_body(repeats, fn_name='_some_name'):
 
 class Tests(unittest.TestCase):
   """All of our tests for redact_profile."""
+
   def test_no_input_works(self):
     self.assertEqual(_redact(''), '')
 
@@ -93,13 +95,13 @@ class Tests(unittest.TestCase):
 
     result_file = '\n'.join(kept_lines) + '\n'
 
-    lines = _generate_repeated_function_body(_redact_limit,
-                                             fn_name='_discard_me')
+    lines = _generate_repeated_function_body(
+        _redact_limit, fn_name='_discard_me')
     self.assertEqual(_redact(kept_lines + lines), result_file)
     self.assertEqual(_redact(lines + kept_lines), result_file)
 
-    more_lines = _generate_repeated_function_body(_redact_limit,
-                                                  fn_name='_and_discard_me')
+    more_lines = _generate_repeated_function_body(
+        _redact_limit, fn_name='_and_discard_me')
     self.assertEqual(_redact(lines + kept_lines + more_lines), result_file)
     self.assertEqual(_redact(lines + more_lines), '')
 
diff --git a/afdo_redaction/remove_indirect_calls.py b/afdo_redaction/remove_indirect_calls.py
index b879b2f0..0dc15077 100755
--- a/afdo_redaction/remove_indirect_calls.py
+++ b/afdo_redaction/remove_indirect_calls.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright 2019 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -21,7 +21,6 @@ from __future__ import division, print_function
 
 import argparse
 import re
-import sys
 
 
 def _remove_indirect_call_targets(lines):
diff --git a/afdo_redaction/remove_indirect_calls_test.py b/afdo_redaction/remove_indirect_calls_test.py
index 1499af25..164b284f 100755
--- a/afdo_redaction/remove_indirect_calls_test.py
+++ b/afdo_redaction/remove_indirect_calls_test.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright 2019 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -11,12 +11,12 @@ from __future__ import print_function
 import io
 import unittest
 
-import remove_indirect_calls
+from afdo_redaction import remove_indirect_calls
 
 
 def _run_test(input_lines):
-  input_buf = io.BytesIO('\n'.join(input_lines))
-  output_buf = io.BytesIO()
+  input_buf = io.StringIO('\n'.join(input_lines))
+  output_buf = io.StringIO()
   remove_indirect_calls.run(input_buf, output_buf)
   return output_buf.getvalue().splitlines()
 
diff --git a/afdo_tools/bisection/afdo_prof_analysis.py b/afdo_tools/bisection/afdo_prof_analysis.py
index 36531106..94e5366b 100755
--- a/afdo_tools/bisection/afdo_prof_analysis.py
+++ b/afdo_tools/bisection/afdo_prof_analysis.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright 2019 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -109,7 +109,7 @@ class DeciderState(object):
                    self.state_file)
       return
 
-    with open(self.state_file) as f:
+    with open(self.state_file, encoding='utf-8') as f:
       try:
         data = json.load(f)
       except:
@@ -127,7 +127,7 @@ class DeciderState(object):
   def save_state(self):
     state = {'seed': self.seed, 'accumulated_results': self.accumulated_results}
     tmp_file = self.state_file + '.new'
-    with open(tmp_file, 'w') as f:
+    with open(tmp_file, 'w', encoding='utf-8') as f:
       json.dump(state, f, indent=2)
     os.rename(tmp_file, self.state_file)
     logging.info('Logged state to %s...', self.state_file)
@@ -270,7 +270,7 @@ def range_search(decider, good, bad, common_funcs, lo, hi):
   def find_upper_border(good_copy, funcs, lo, hi, last_bad_val=None):
     """Finds the upper border of problematic range."""
     mid = average(lo, hi)
-    if mid == lo or mid == hi:
+    if mid in (lo, hi):
       return last_bad_val or hi
 
     for func in funcs[lo:mid]:
@@ -288,7 +288,7 @@ def range_search(decider, good, bad, common_funcs, lo, hi):
   def find_lower_border(good_copy, funcs, lo, hi, last_bad_val=None):
     """Finds the lower border of problematic range."""
     mid = average(lo, hi)
-    if mid == lo or mid == hi:
+    if mid in (lo, hi):
       return last_bad_val or lo
 
     for func in funcs[lo:mid]:
@@ -428,7 +428,7 @@ def main(flags):
       'good_only_functions': gnb_result,
       'bad_only_functions': bng_result
   }
-  with open(flags.analysis_output_file, 'wb') as f:
+  with open(flags.analysis_output_file, 'w', encoding='utf-8') as f:
     json.dump(results, f, indent=2)
   if flags.remove_state_on_completion:
     os.remove(flags.state_file)
diff --git a/afdo_tools/bisection/afdo_prof_analysis_e2e_test.py b/afdo_tools/bisection/afdo_prof_analysis_e2e_test.py
index 85c1c175..b293b8aa 100755
--- a/afdo_tools/bisection/afdo_prof_analysis_e2e_test.py
+++ b/afdo_tools/bisection/afdo_prof_analysis_e2e_test.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright 2019 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -15,13 +15,13 @@ import tempfile
 import unittest
 from datetime import date
 
-import afdo_prof_analysis as analysis
+from afdo_tools.bisection import afdo_prof_analysis as analysis
 
 
 class ObjectWithFields(object):
   """Turns kwargs given to the constructor into fields on an object.
 
-  Example usage:
+  Examples:
     x = ObjectWithFields(a=1, b=2)
     assert x.a == 1
     assert x.b == 2
diff --git a/afdo_tools/bisection/afdo_prof_analysis_test.py b/afdo_tools/bisection/afdo_prof_analysis_test.py
index 7bd3050c..245edc33 100755
--- a/afdo_tools/bisection/afdo_prof_analysis_test.py
+++ b/afdo_tools/bisection/afdo_prof_analysis_test.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright 2019 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -8,12 +8,12 @@
 
 from __future__ import print_function
 
-import afdo_prof_analysis as analysis
-
 import random
-import StringIO
+import io
 import unittest
 
+from afdo_tools.bisection import afdo_prof_analysis as analysis
+
 
 class AfdoProfAnalysisTest(unittest.TestCase):
   """Class for testing AFDO Profile Analysis"""
@@ -33,17 +33,17 @@ class AfdoProfAnalysisTest(unittest.TestCase):
   analysis.random.seed(5)  # 5 is an arbitrary choice. For consistent testing
 
   def test_text_to_json(self):
-    test_data = StringIO.StringIO('deflate_slow:87460059:3\n'
-                                  ' 3: 24\n'
-                                  ' 14: 54767\n'
-                                  ' 15: 664 fill_window:22\n'
-                                  ' 16: 661\n'
-                                  ' 19: 637\n'
-                                  ' 41: 36692 longest_match:36863\n'
-                                  ' 44: 36692\n'
-                                  ' 44.2: 5861\n'
-                                  ' 46: 13942\n'
-                                  ' 46.1: 14003\n')
+    test_data = io.StringIO('deflate_slow:87460059:3\n'
+                            ' 3: 24\n'
+                            ' 14: 54767\n'
+                            ' 15: 664 fill_window:22\n'
+                            ' 16: 661\n'
+                            ' 19: 637\n'
+                            ' 41: 36692 longest_match:36863\n'
+                            ' 44: 36692\n'
+                            ' 44.2: 5861\n'
+                            ' 46: 13942\n'
+                            ' 46.1: 14003\n')
     expected = {
         'deflate_slow': ':87460059:3\n'
                         ' 3: 24\n'
@@ -115,7 +115,7 @@ class AfdoProfAnalysisTest(unittest.TestCase):
                                           self.bad_items, common_funcs, 0,
                                           len(common_funcs))
 
-    self.assertEquals(['func_a', 'func_b'], problem_range)
+    self.assertEqual(['func_a', 'func_b'], problem_range)
 
   def test_check_good_not_bad(self):
     func_in_good = 'func_c'
diff --git a/afdo_tools/generate_afdo_from_tryjob.py b/afdo_tools/generate_afdo_from_tryjob.py
index b8a2d669..3ed578ea 100755
--- a/afdo_tools/generate_afdo_from_tryjob.py
+++ b/afdo_tools/generate_afdo_from_tryjob.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright 2019 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -115,7 +115,7 @@ def main():
       '--tryjob',
       required=True,
       type=_tryjob_arg,
-      help='Path to our tryjob\'s artifacts. Accepts a gs:// path, pantheon '
+      help="Path to our tryjob's artifacts. Accepts a gs:// path, pantheon "
       'link, or tryjob ID, e.g. R75-11965.0.0-b3648595. In the last case, '
       'the assumption is that you ran a chell-chrome-pfq-tryjob.')
   parser.add_argument(
@@ -127,7 +127,7 @@ def main():
       '-k',
       '--keep_artifacts_on_failure',
       action='store_true',
-      help='Don\'t remove the tempdir on failure')
+      help="Don't remove the tempdir on failure")
   args = parser.parse_args()
 
   if not distutils.spawn.find_executable(_CREATE_LLVM_PROF):
diff --git a/afdo_tools/run_afdo_tryjob.py b/afdo_tools/run_afdo_tryjob.py
index de45af0b..e14cd918 100755
--- a/afdo_tools/run_afdo_tryjob.py
+++ b/afdo_tools/run_afdo_tryjob.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright 2019 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -94,7 +94,7 @@ def main():
   user_patches = args.patch
 
   if tag_profiles_with_current_time and use_afdo_generation_stage:
-    raise ValueError('You can\'t tag profiles with the time + have '
+    raise ValueError("You can't tag profiles with the time + have "
                      'afdo-generate')
 
   if not tag_profiles_with_current_time and not use_afdo_generation_stage:
diff --git a/compiler_wrapper/build.py b/compiler_wrapper/build.py
index 6b647714..4257abfc 100755
--- a/compiler_wrapper/build.py
+++ b/compiler_wrapper/build.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright 2019 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -52,7 +52,7 @@ def read_version(build_dir):
       return r.read()
 
   last_commit_msg = subprocess.check_output(
-      ['git', '-C', build_dir, 'log', '-1', '--pretty=%B'])
+      ['git', '-C', build_dir, 'log', '-1', '--pretty=%B'], encoding='utf-8')
   # Use last found change id to support reverts as well.
   change_ids = re.findall(r'Change-Id: (\w+)', last_commit_msg)
   if not change_ids:
diff --git a/compiler_wrapper/bundle.py b/compiler_wrapper/bundle.py
index c1fa53e0..173625f4 100755
--- a/compiler_wrapper/bundle.py
+++ b/compiler_wrapper/bundle.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright 2019 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -32,7 +32,7 @@ def copy_files(input_dir, output_dir):
 
 def read_change_id(input_dir):
   last_commit_msg = subprocess.check_output(
-      ['git', '-C', input_dir, 'log', '-1', '--pretty=%B'])
+      ['git', '-C', input_dir, 'log', '-1', '--pretty=%B'], encoding='utf-8')
   # Use last found change id to support reverts as well.
   change_ids = re.findall(r'Change-Id: (\w+)', last_commit_msg)
   if not change_ids:
@@ -41,14 +41,15 @@ def read_change_id(input_dir):
 
 
 def write_readme(input_dir, output_dir, change_id):
-  with open(os.path.join(input_dir, 'bundle.README'), 'r') as r, \
-       open(os.path.join(output_dir, 'README'), 'w') as w:
-    content = r.read()
-    w.write(content.format(change_id=change_id))
+  with open(
+      os.path.join(input_dir, 'bundle.README'), 'r', encoding='utf-8') as r:
+    with open(os.path.join(output_dir, 'README'), 'w', encoding='utf-8') as w:
+      content = r.read()
+      w.write(content.format(change_id=change_id))
 
 
 def write_version(output_dir, change_id):
-  with open(os.path.join(output_dir, 'VERSION'), 'w') as w:
+  with open(os.path.join(output_dir, 'VERSION'), 'w', encoding='utf-8') as w:
     w.write(change_id)
 
 
diff --git a/debug_info_test/check_cus.py b/debug_info_test/check_cus.py
index f68fe9cb..d3cd6365 100644
--- a/debug_info_test/check_cus.py
+++ b/debug_info_test/check_cus.py
@@ -1,7 +1,12 @@
+# -*- coding: utf-8 -*-
 # Copyright 2018 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+"""check compile units."""
+
+from __future__ import print_function
+
 import os
 import subprocess
 
@@ -9,59 +14,62 @@ import check_ngcc
 
 cu_checks = [check_ngcc.not_by_gcc]
 
+
 def check_compile_unit(dso_path, producer, comp_path):
-    """check all compiler flags used to build the compile unit.
+  """check all compiler flags used to build the compile unit.
+
+  Args:
+    dso_path: path to the elf/dso.
+    producer: DW_AT_producer contains the compiler command line.
+    comp_path: DW_AT_comp_dir + DW_AT_name.
 
-    Args:
-        dso_path: path to the elf/dso
-        producer: DW_AT_producer contains the compiler command line.
-        comp_path: DW_AT_comp_dir + DW_AT_name
+  Returns:
+    A set of failed tests.
+  """
+  failed = set()
+  for c in cu_checks:
+    if not c(dso_path, producer, comp_path):
+      failed.add(c.__module__)
 
-    Returns:
-        A set of failed tests.
-    """
-    failed = set()
-    for c in cu_checks:
-        if not c(dso_path, producer, comp_path):
-            failed.add(c.__module__)
+  return failed
 
-    return failed
 
 def check_compile_units(dso_path):
-    """check all compile units in the given dso.
-
-    Args:
-        dso_path: path to the dso
-    Return:
-        True if everything looks fine otherwise False.
-    """
-
-    failed = set()
-    producer = ''
-    comp_path = ''
-
-    readelf = subprocess.Popen(['readelf', '--debug-dump=info',
-                                '--dwarf-depth=1', dso_path],
-                                stdout=subprocess.PIPE,
-                                stderr=open(os.devnull, 'w'))
-    for l in readelf.stdout:
-        if 'DW_TAG_compile_unit' in l:
-            if producer:
-                failed = failed.union(check_compile_unit(dso_path, producer,
-                                                         comp_path))
-            producer = ''
-            comp_path = ''
-        elif 'DW_AT_producer' in l:
-            producer = l
-        elif 'DW_AT_name' in l:
-            comp_path = os.path.join(comp_path, l.split(':')[-1].strip())
-        elif 'DW_AT_comp_dir' in l:
-            comp_path = os.path.join(l.split(':')[-1].strip(), comp_path)
-    if producer:
+  """check all compile units in the given dso.
+
+  Args:
+    dso_path: path to the dso.
+
+  Returns:
+    True if everything looks fine otherwise False.
+  """
+
+  failed = set()
+  producer = ''
+  comp_path = ''
+
+  readelf = subprocess.Popen(
+      ['readelf', '--debug-dump=info', '--dwarf-depth=1', dso_path],
+      stdout=subprocess.PIPE,
+      stderr=open(os.devnull, 'w'),
+      encoding='utf-8')
+  for l in readelf.stdout:
+    if 'DW_TAG_compile_unit' in l:
+      if producer:
         failed = failed.union(check_compile_unit(dso_path, producer, comp_path))
+      producer = ''
+      comp_path = ''
+    elif 'DW_AT_producer' in l:
+      producer = l
+    elif 'DW_AT_name' in l:
+      comp_path = os.path.join(comp_path, l.split(':')[-1].strip())
+    elif 'DW_AT_comp_dir' in l:
+      comp_path = os.path.join(l.split(':')[-1].strip(), comp_path)
+  if producer:
+    failed = failed.union(check_compile_unit(dso_path, producer, comp_path))
 
-    if failed:
-        print('%s failed check: %s' % (dso_path, ' '.join(failed)))
-        return False
+  if failed:
+    print('%s failed check: %s' % (dso_path, ' '.join(failed)))
+    return False
 
-    return True
+  return True
diff --git a/debug_info_test/check_exist.py b/debug_info_test/check_exist.py
index 5e7cce19..dbb89127 100644
--- a/debug_info_test/check_exist.py
+++ b/debug_info_test/check_exist.py
@@ -1,90 +1,102 @@
+# -*- coding: utf-8 -*-
 # Copyright 2018 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+"""check whether intended components exists in the given dso."""
+
+from __future__ import print_function
+
 import os
 import subprocess
 
 from whitelist import is_whitelisted
 
+
 def check_debug_info(dso_path, readelf_content):
-    """check whether debug info section exists in the elf file.
+  """Check whether debug info section exists in the elf file.
+
+  Args:
+    dso_path: path to the dso.
+    readelf_content: debug info dumped by command readelf.
 
-    Args:
-        readelf: debug info dumped by command readelf
+  Returns:
+    True if debug info section exists, otherwise False.
+  """
 
-    Returns:
-        True if debug info section exists, otherwise False.
-    """
+  # Return True if it is whitelisted
+  if is_whitelisted('exist_debug_info', dso_path):
+    return True
 
-    # Return True if it is whitelisted
-    if is_whitelisted('exist_debug_info', dso_path):
-        return True
+  for l in readelf_content:
+    if 'debug_info' in l:
+      return True
+  return False
 
-    for l in readelf_content:
-        if 'debug_info' in l:
-          return True
-    return False
 
 def check_producer(dso_path, readelf_content):
-    """check whether DW_AT_producer exists in each compile unit.
-
-    Args:
-        readelf: debug info dumped by command readelf
-
-    Returns:
-        True if DW_AT_producer exists in each compile unit, otherwise False.
-        Notice: If no compile unit in DSO, also return True.
-    """
-
-    # Return True if it is whitelisted
-    if is_whitelisted('exist_producer', dso_path):
-        return True
-
-    # Indicate if there is a producer under each cu
-    cur_producer = False
-
-    first_cu = True
-    producer_exist = True
-
-    for l in readelf_content:
-        if 'DW_TAG_compile_unit' in l:
-            if not first_cu and not cur_producer:
-                producer_exist = False
-                break
-            first_cu = False
-            cur_producer = False
-        elif 'DW_AT_producer' in l:
-            cur_producer = True
-
-    # Check whether last producer of compile unit exists in the elf,
-    # also return True if no cu in the DSO.
-    if not first_cu and not cur_producer:
+  """Check whether DW_AT_producer exists in each compile unit.
+
+  Args:
+    dso_path: path to the dso.
+    readelf_content: debug info dumped by command readelf.
+
+  Returns:
+    True if DW_AT_producer exists in each compile unit, otherwise False.
+    Notice: If no compile unit in DSO, also return True.
+  """
+
+  # Return True if it is whitelisted
+  if is_whitelisted('exist_producer', dso_path):
+    return True
+
+  # Indicate if there is a producer under each cu
+  cur_producer = False
+
+  first_cu = True
+  producer_exist = True
+
+  for l in readelf_content:
+    if 'DW_TAG_compile_unit' in l:
+      if not first_cu and not cur_producer:
         producer_exist = False
+        break
+      first_cu = False
+      cur_producer = False
+    elif 'DW_AT_producer' in l:
+      cur_producer = True
+
+  # Check whether last producer of compile unit exists in the elf,
+  # also return True if no cu in the DSO.
+  if not first_cu and not cur_producer:
+    producer_exist = False
+
+  return producer_exist
 
-    return producer_exist
 
 def check_exist_all(dso_path):
-    """check whether intended components exists in the given dso.
+  """check whether intended components exists in the given dso.
 
-    Args:
-        dso_path: path to the dso
-    Return:
-        True if everything looks fine otherwise False.
-    """
+  Args:
+    dso_path: path to the dso.
 
-    readelf = subprocess.Popen(['readelf', '--debug-dump=info',
-                                '--dwarf-depth=1', dso_path],
-                                stdout=subprocess.PIPE,
-                                stderr=open(os.devnull, 'w'))
-    readelf_content = list(readelf.stdout)
+  Returns:
+    True if everything looks fine otherwise False.
+  """
 
-    exist_checks = [check_debug_info, check_producer]
+  readelf = subprocess.Popen(
+      ['readelf', '--debug-dump=info', '--dwarf-depth=1', dso_path],
+      stdout=subprocess.PIPE,
+      stderr=open(os.devnull, 'w'),
+      encoding='utf-8')
+  readelf_content = list(readelf.stdout)
 
-    for e in exist_checks:
-        if not e(dso_path, readelf_content):
-            check_failed = e.__module__ + ': ' + e.__name__
-            print('%s failed check: %s' % (dso_path, check_failed))
-            return False
+  exist_checks = [check_debug_info, check_producer]
 
-    return True
+  for e in exist_checks:
+    if not e(dso_path, readelf_content):
+      check_failed = e.__module__ + ': ' + e.__name__
+      print('%s failed check: %s' % (dso_path, check_failed))
+      return False
+
+  return True
diff --git a/debug_info_test/check_icf.py b/debug_info_test/check_icf.py
index 4ac67dbd..a46968e7 100644
--- a/debug_info_test/check_icf.py
+++ b/debug_info_test/check_icf.py
@@ -1,47 +1,53 @@
+# -*- coding: utf-8 -*-
 # Copyright 2018 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+"""check whether chrome was built with identical code folding."""
+
+from __future__ import print_function
+
 import os
 import re
 import subprocess
 
+
 def check_identical_code_folding(dso_path):
-    """check whether chrome was built with identical code folding.
-
-    Args:
-        dso_path: path to the dso
-    Return:
-        False if the dso is chrome and it was not built with icf,
-        True otherwise.
-    """
-
-    if not dso_path.endswith('/chrome.debug'):
-        return True
-
-    # Run 'nm' on the chrome binary and read the output.
-    nm = subprocess.Popen(['nm', dso_path],
-                          stdout=subprocess.PIPE,
-                          stderr=open(os.devnull, 'w'))
-    nm_output, _ = nm.communicate()
-
-    # Search for addresses of text symbols.
-    text_addresses = re.findall('^[0-9a-f]+[ ]+[tT] ',
-                                nm_output,
-                                re.MULTILINE)
-
-    # Calculate number of text symbols in chrome binary.
-    num_text_addresses = len(text_addresses)
-
-    # Calculate number of unique text symbols in chrome binary.
-    num_unique_text_addresses = len(set(text_addresses))
-
-    # Check that the number of duplicate symbols is at least 10,000.
-    #   - https://crbug.com/813272#c18
-    if num_text_addresses-num_unique_text_addresses >= 10000:
-        return True
-
-    print('%s was not built with ICF' % dso_path)
-    print('    num_text_addresses = %d' % num_text_addresses)
-    print('    num_unique_text_addresses = %d' % num_unique_text_addresses)
-    return False
+  """check whether chrome was built with identical code folding.
+
+  Args:
+    dso_path: path to the dso.
+
+  Returns:
+    False if the dso is chrome and it was not built with icf,
+    True otherwise.
+  """
+
+  if not dso_path.endswith('/chrome.debug'):
+    return True
+
+  # Run 'nm' on the chrome binary and read the output.
+  nm = subprocess.Popen(['nm', dso_path],
+                        stdout=subprocess.PIPE,
+                        stderr=open(os.devnull, 'w'),
+                        encoding='utf-8')
+  nm_output, _ = nm.communicate()
+
+  # Search for addresses of text symbols.
+  text_addresses = re.findall('^[0-9a-f]+[ ]+[tT] ', nm_output, re.MULTILINE)
+
+  # Calculate number of text symbols in chrome binary.
+  num_text_addresses = len(text_addresses)
+
+  # Calculate number of unique text symbols in chrome binary.
+  num_unique_text_addresses = len(set(text_addresses))
+
+  # Check that the number of duplicate symbols is at least 10,000.
+  #   - https://crbug.com/813272#c18
+  if num_text_addresses - num_unique_text_addresses >= 10000:
+    return True
+
+  print('%s was not built with ICF' % dso_path)
+  print('    num_text_addresses = %d' % num_text_addresses)
+  print('    num_unique_text_addresses = %d' % num_unique_text_addresses)
+  return False
diff --git a/debug_info_test/check_ngcc.py b/debug_info_test/check_ngcc.py
index eecbb85e..501bb988 100644
--- a/debug_info_test/check_ngcc.py
+++ b/debug_info_test/check_ngcc.py
@@ -1,26 +1,30 @@
+# -*- coding: utf-8 -*-
 # Copyright 2018 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+"""Check whether the compile unit is not built by gcc."""
+
+from __future__ import print_function
+
 from whitelist import is_whitelisted
 
-def not_by_gcc(dso_path, producer, comp_path):
-    """Check whether the compile unit is not built by gcc.
 
-    Args:
-        dso_path: path to the elf/dso
-        producer: DW_AT_producer contains the compiler command line.
-        comp_path: DW_AT_comp_dir + DW_AT_name
+def not_by_gcc(dso_path, producer, comp_path):
+  """Check whether the compile unit is not built by gcc.
 
-    Returns:
-        False if compiled by gcc otherwise True
-    """
-    if is_whitelisted('ngcc_comp_path', comp_path):
-        return True
+  Args:
+    dso_path: path to the elf/dso.
+    producer: DW_AT_producer contains the compiler command line.
+    comp_path: DW_AT_comp_dir + DW_AT_name.
 
-    if is_whitelisted('ngcc_dso_path', dso_path):
-        return True
+  Returns:
+    False if compiled by gcc otherwise True.
+  """
+  if is_whitelisted('ngcc_comp_path', comp_path):
+    return True
 
-    if 'GNU C' in producer:
-        return False
+  if is_whitelisted('ngcc_dso_path', dso_path):
     return True
+
+  return 'GNU C' not in producer
diff --git a/debug_info_test/debug_info_test.py b/debug_info_test/debug_info_test.py
index 4839e69c..ae7e9f48 100755
--- a/debug_info_test/debug_info_test.py
+++ b/debug_info_test/debug_info_test.py
@@ -1,9 +1,13 @@
-#!/usr/bin/python2
-
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
 # Copyright 2018 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+"""Test for debug info."""
+
+from __future__ import print_function
+
 import os
 import subprocess
 import sys
@@ -12,46 +16,52 @@ import check_icf
 import check_cus
 import check_exist
 
-elf_checks = [check_exist.check_exist_all,
-              check_cus.check_compile_units,
-              check_icf.check_identical_code_folding]
+elf_checks = [
+    check_exist.check_exist_all, check_cus.check_compile_units,
+    check_icf.check_identical_code_folding
+]
+
 
 def scanelf(root):
-    """find ELFs in root
+  """Find ELFs in root.
+
+  Args:
+    root: root dir to start with the search.
+
+  Returns:
+    Filenames of ELFs in root.
+  """
+  p = subprocess.Popen(['scanelf', '-y', '-B', '-F', '%F', '-R', root],
+                       stdout=subprocess.PIPE,
+                       encoding='utf-8')
+  return [l.strip() for l in p.stdout]
 
-    Args:
-        root: root dir to start with the search.
-    Returns:
-        Filenames of ELFs in root.
-    """
-    p = subprocess.Popen(['scanelf', '-y', '-B', '-F', '%F', '-R', root],
-                         stdout=subprocess.PIPE)
-    return [l.strip() for l in p.stdout]
 
 def Main(argv):
-    if len(argv) < 2:
-        print('usage: %s [file|dir]')
-        return 1
-
-    files = []
-    cand = argv[1]
-    if os.path.isfile(cand):
-        files = [cand]
-    elif os.path.isdir(cand):
-        files = scanelf(cand)
-    else:
-        print('usage: %s [file|dir]')
-        return 1
-
-    failed = False
-    for f in files:
-        for c in elf_checks:
-            if not c(f):
-                failed = True
-
-    if failed:
-        return 1
-    return 0
+  if len(argv) < 2:
+    print('usage: %s [file|dir]')
+    return 1
+
+  files = []
+  cand = argv[1]
+  if os.path.isfile(cand):
+    files = [cand]
+  elif os.path.isdir(cand):
+    files = scanelf(cand)
+  else:
+    print('usage: %s [file|dir]')
+    return 1
+
+  failed = False
+  for f in files:
+    for c in elf_checks:
+      if not c(f):
+        failed = True
+
+  if failed:
+    return 1
+  return 0
+
 
 if __name__ == '__main__':
-    sys.exit(Main(sys.argv))
+  sys.exit(Main(sys.argv))
diff --git a/debug_info_test/whitelist.py b/debug_info_test/whitelist.py
index 383fcc3d..b53387a8 100644
--- a/debug_info_test/whitelist.py
+++ b/debug_info_test/whitelist.py
@@ -1,11 +1,17 @@
+# -*- coding: utf-8 -*-
 # Copyright 2018 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+"""Whitelist functions."""
+
+from __future__ import print_function
+
 import os
 import glob
 import re
 
+
 # Matching a string of length m in an NFA of size n is O(mn^2), but the
 # performance also depends largely on the implementation. It appears to be fast
 # enough according to the tests.
@@ -13,45 +19,50 @@ import re
 # The performance bottleneck of this script is readelf. Unless this becomes
 # slower than readelf, don't waste time here.
 def is_whitelisted(list_name, pattern):
-    """chech whether the given pattern is specified in the whitelist.
+  """Check whether the given pattern is specified in the whitelist.
+
+  Args:
+    list_name: name of the whitelist.
+    pattern: the target string.
+
+  Returns:
+    True if matched otherwise False.
+  """
+  return pattern and whitelists[list_name].match(pattern)
 
-    Args:
-        list_name: name of the whitelist
-        pattern: the target string
-    Returns:
-        True if matched otherwise False
-    """
-    return pattern and whitelists[list_name].match(pattern)
 
 def prepare_whitelist(patterns):
-    """Join and compile the re patterns.
+  """Join and compile the re patterns.
+
+  Args:
+    patterns: regex patterns.
+
+  Returns:
+    A compiled re object.
+  """
+  return re.compile('|'.join(patterns))
 
-    Args:
-        patterns: regex patterns.
-    Return:
-        A compiled re object
-    """
-    return re.compile('|'.join(patterns))
 
 def load_whitelists(dirname):
-    """Load whitelists under dirname.
-
-    A whitelist ends with .whitelist.
-
-    Args:
-        dirname: path to the dir.
-    Returns:
-        A dictionary of 'filename' -> whitelist matcher.
-    """
-    wlist = {}
-    for fn in glob.glob(os.path.join(dirname, '*.whitelist')):
-        key = os.path.splitext(os.path.basename(fn))[0]
-        with open(fn, 'r') as f:
-            patterns = f.read().splitlines()
-            patterns = [l for l in patterns if l != '']
-            patterns = [l for l in patterns if l[0] != '#']
-        wlist[key] = prepare_whitelist(patterns)
-    return wlist
+  """Load whitelists under dirname.
+
+  A whitelist ends with .whitelist.
+
+  Args:
+    dirname: path to the dir.
+
+  Returns:
+    A dictionary of 'filename' -> whitelist matcher.
+  """
+  wlist = {}
+  for fn in glob.glob(os.path.join(dirname, '*.whitelist')):
+    key = os.path.splitext(os.path.basename(fn))[0]
+    with open(fn, 'r', encoding='utf-8') as f:
+      patterns = f.read().splitlines()
+      patterns = [l for l in patterns if l != '']
+      patterns = [l for l in patterns if l[0] != '#']
+    wlist[key] = prepare_whitelist(patterns)
+  return wlist
 
 
 whitelists = load_whitelists(os.path.dirname(__file__))
diff --git a/go/chromeos/setup_chromeos_testing.py b/go/chromeos/setup_chromeos_testing.py
index b679ddfc..8b535538 100755
--- a/go/chromeos/setup_chromeos_testing.py
+++ b/go/chromeos/setup_chromeos_testing.py
@@ -1,7 +1,9 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
-#
-# Copyright 2018 Google Inc. All Rightes Reserved
+# Copyright 2020 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
 """Generate board-specific scripts for Go compiler testing."""
 
 from __future__ import print_function
@@ -73,7 +75,7 @@ def log(msg):
 
 
 def WriteFile(file_content, file_name):
-  with open(file_name, 'w') as out_file:
+  with open(file_name, 'w', encoding='utf-8') as out_file:
     out_file.write(file_content)
 
 
@@ -82,7 +84,7 @@ def GenerateGoHelperScripts(ce, arm_board, x86_board, chromeos_root):
   names = {
       'x86_64': x86_board,
       'arm64': arm_board,
-      'arm32': ("%s32" % arm_board)
+      'arm32': ('%s32' % arm_board)
   }
 
   toolchain_dir = os.path.join(chromeos_root, 'src', 'third_party',
@@ -93,17 +95,17 @@ def GenerateGoHelperScripts(ce, arm_board, x86_board, chromeos_root):
     toolchain = CROS_TOOLCHAIN_DATA[k]
     glibc = GLIBC_DATA[k]
 
-    base_file = os.path.join(toolchain_dir, ("go_%s" % name))
+    base_file = os.path.join(toolchain_dir, ('go_%s' % name))
     base_file_content = BASE_TEMPLATE % (name, arch, arch, toolchain, toolchain,
                                          toolchain)
     WriteFile(base_file_content, base_file)
-    cmd = "chmod 755 %s" % base_file
+    cmd = 'chmod 755 %s' % base_file
     ce.RunCommand(cmd)
 
-    exec_file = os.path.join(toolchain_dir, ("go_%s_exec" % name))
+    exec_file = os.path.join(toolchain_dir, ('go_%s_exec' % name))
     exec_file_content = EXEC_TEMPLATE % (name, arch, glibc, name)
     WriteFile(exec_file_content, exec_file)
-    cmd = "chmod 755 %s" % exec_file
+    cmd = 'chmod 755 %s' % exec_file
     ce.RunCommand(cmd)
 
   return 0
@@ -111,7 +113,7 @@ def GenerateGoHelperScripts(ce, arm_board, x86_board, chromeos_root):
 
 def UpdateChrootSshConfig(ce, arm_board, arm_dut, x86_board, x86_dut,
                           chromeos_root):
-  log("Entering UpdateChrootSshConfig")
+  log('Entering UpdateChrootSshConfig')
   # Copy testing_rsa to .ssh and set file protections properly.
   user = getpass.getuser()
   ssh_dir = os.path.join(chromeos_root, 'chroot', 'home', user, '.ssh')
@@ -133,22 +135,22 @@ def UpdateChrootSshConfig(ce, arm_board, arm_dut, x86_board, x86_dut,
       print('Cannot find %s; you will need to update testing_rsa by hand.' %
             src_file)
   else:
-    log("testing_rsa exists already.")
+    log('testing_rsa exists already.')
 
   # Save ~/.ssh/config file, if not already done.
-  config_file = os.path.expanduser("~/.ssh/config")
+  config_file = os.path.expanduser('~/.ssh/config')
   saved_config_file = os.path.join(
-      os.path.expanduser("~/.ssh"), "config.save.go-scripts")
+      os.path.expanduser('~/.ssh'), 'config.save.go-scripts')
   if not os.path.exists(saved_config_file):
-    cmd = "cp %s %s" % (config_file, saved_config_file)
+    cmd = 'cp %s %s' % (config_file, saved_config_file)
     ret = ce.RunCommand(cmd)
     if ret != SUCCESS:
-      print("Error making save copy of ~/.ssh/config. Exiting...")
+      print('Error making save copy of ~/.ssh/config. Exiting...')
       sys.exit(1)
 
   # Update ~/.ssh/config file
-  log("Reading ssh config file")
-  with open(config_file, "r") as input_file:
+  log('Reading ssh config file')
+  with open(config_file, 'r') as input_file:
     config_lines = input_file.read()
 
   x86_host_config = CONFIG_TEMPLATE % (x86_board, x86_dut)
@@ -158,7 +160,7 @@ def UpdateChrootSshConfig(ce, arm_board, arm_dut, x86_board, x86_dut,
   config_lines += x86_host_config
   config_lines += arm_host_config
 
-  log("Writing ~/.ssh/config")
+  log('Writing ~/.ssh/config')
   WriteFile(config_lines, config_file)
 
   return 0
@@ -170,27 +172,27 @@ def CleanUp(ce, x86_board, arm_board, chromeos_root):
   names = {
       'x86_64': x86_board,
       'arm64': arm_board,
-      'arm32': ("%s32" % arm_board)
+      'arm32': ('%s32' % arm_board)
   }
 
   toolchain_dir = os.path.join(chromeos_root, 'src', 'third_party',
                                'toolchain-utils', 'go', 'chromeos')
   for k in keys:
     name = names[k]
-    base_file = os.path.join(toolchain_dir, ("go_%s" % name))
-    exec_file = os.path.join(toolchain_dir, ("go_%s_exec" % name))
+    base_file = os.path.join(toolchain_dir, ('go_%s' % name))
+    exec_file = os.path.join(toolchain_dir, ('go_%s_exec' % name))
     cmd = ('rm -f %s; rm -f %s' % (base_file, exec_file))
     ce.RunCommand(cmd)
 
   # Restore saved config_file
-  config_file = os.path.expanduser("~/.ssh/config")
+  config_file = os.path.expanduser('~/.ssh/config')
   saved_config_file = os.path.join(
-      os.path.expanduser("~/.ssh"), "config.save.go-scripts")
+      os.path.expanduser('~/.ssh'), 'config.save.go-scripts')
   if not os.path.exists(saved_config_file):
-    print("Could not find file: %s; unable to restore ~/.ssh/config ." %
+    print('Could not find file: %s; unable to restore ~/.ssh/config .' %
           saved_config_file)
   else:
-    cmd = "mv %s %s" % (saved_config_file, config_file)
+    cmd = 'mv %s %s' % (saved_config_file, config_file)
     ce.RunCommand(cmd)
 
   return 0
@@ -219,7 +221,7 @@ def Main(argv):
     DEBUG = True
 
   if not os.path.exists(options.chromeos_root):
-    print("Invalid ChromeOS Root: %s" % options.chromeos_root)
+    print('Invalid ChromeOS Root: %s' % options.chromeos_root)
 
   ce = command_executer.GetCommandExecuter()
   all_good = True
@@ -245,6 +247,6 @@ def Main(argv):
   return 0
 
 
-if __name__ == "__main__":
+if __name__ == '__main__':
   val = Main(sys.argv)
   sys.exit(val)
diff --git a/heatmaps/heat_map.py b/heatmaps/heat_map.py
index 2fd742d2..a989ab70 100755
--- a/heatmaps/heat_map.py
+++ b/heatmaps/heat_map.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright 2015 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -15,7 +15,7 @@ import sys
 import tempfile
 
 from cros_utils import command_executer
-import heatmap_generator
+from heatmaps import heatmap_generator
 
 
 def IsARepoRoot(directory):
diff --git a/heatmaps/heat_map_test.py b/heatmaps/heat_map_test.py
index 21f90d41..ad62cd91 100755
--- a/heatmaps/heat_map_test.py
+++ b/heatmaps/heat_map_test.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 #
 # Copyright 2019 The Chromium OS Authors. All rights reserved.
@@ -9,14 +9,15 @@
 
 from __future__ import print_function
 
-import mock
+import unittest.mock as mock
 import unittest
 
 import os
 
 from cros_utils import command_executer
 
-import heat_map
+from heatmaps import heat_map
+from heatmaps import heatmap_generator
 
 
 def make_heatmap(chromeos_root='/path/to/fake/chromeos_root/',
@@ -41,7 +42,7 @@ def fake_generate_perf_report_exception(_):
 class HeatmapTest(unittest.TestCase):
   """All of our tests for heat_map."""
 
-  #pylint: disable=protected-access
+  # pylint: disable=protected-access
   @mock.patch('shutil.copy2')
   @mock.patch('tempfile.mkdtemp')
   def test_EnsureFileInChrootAlreadyInside(self, mock_mkdtemp, mock_copy):
@@ -81,7 +82,7 @@ class HeatmapTest(unittest.TestCase):
     self.assertEqual(heatmap.perf_report,
                      '/fake/chroot/inchroot_path/perf_report.txt')
 
-  @mock.patch('heatmap_generator.HeatmapGenerator')
+  @mock.patch.object(heatmap_generator, 'HeatmapGenerator')
   def test_GetHeatMap(self, mock_heatmap_generator):
     heatmap = make_heatmap()
     heatmap._GetHeatMap(10)
@@ -107,7 +108,7 @@ class HeatmapTest(unittest.TestCase):
       new=fake_generate_perf_report_exception)
   @mock.patch.object(heat_map.HeatMapProducer, '_GetHeatMap')
   @mock.patch.object(heat_map.HeatMapProducer, '_RemoveFiles')
-  @mock.patch('__builtin__.print')
+  @mock.patch('builtins.print')
   def test_Run_with_exception(self, mock_print, mock_remove_files,
                               mock_get_heatmap, mock_ensure_file_in_chroot):
     heatmap = make_heatmap()
diff --git a/heatmaps/heatmap_generator.py b/heatmaps/heatmap_generator.py
index 42fd6352..0dd6ad28 100644
--- a/heatmaps/heatmap_generator.py
+++ b/heatmaps/heatmap_generator.py
@@ -13,7 +13,7 @@ performed by another script perf-to-inst-page.sh). It can also analyze
 the symbol names in hot pages.
 """
 
-from __future__ import print_function
+from __future__ import division, print_function
 
 import bisect
 import collections
@@ -93,10 +93,10 @@ class HeatmapGenerator(object):
     self.max_addr = 1024 * 1024 * 1024
     self.ce = command_executer.GetCommandExecuter(log_level=log_level)
     self.dir = os.path.dirname(os.path.realpath(__file__))
-    with open(perf_report) as f:
+    with open(perf_report, 'r', encoding='utf-8') as f:
       self.perf_report_contents = f.readlines()
     # Write histogram results to a text file, in order to use gnu plot to draw
-    self.hist_temp_output = open('out.txt', 'w')
+    self.hist_temp_output = open('out.txt', 'w', encoding='utf-8')
     self.processes = {}
     self.deleted_processes = {}
     self.count = 0
@@ -277,7 +277,7 @@ class HeatmapGenerator(object):
     if address < self.max_addr:
       self.count += 1
       line = '%d/%d: %d %d' % (pid[0], pid[1], self.count,
-                               address / self.page_size * self.page_size)
+                               address // self.page_size * self.page_size)
       if self.hugepage:
         if self.hugepage.start <= address < self.hugepage.end:
           line += ' hugepage'
@@ -321,7 +321,7 @@ class HeatmapGenerator(object):
     names = [x for x in os.listdir('.') if 'inst-histo' in x and '.txt' in x]
     hist = {}
     for n in names:
-      with open(n) as f:
+      with open(n, encoding='utf-8') as f:
         for l in f.readlines():
           num, addr = l.strip().split(' ')
           assert int(addr) not in hist
@@ -354,7 +354,7 @@ class HeatmapGenerator(object):
       if 't' not in symbol_type and 'T' not in symbol_type:
         # Filter out symbols not in text sections
         continue
-      if len(self.symbol_addresses) == 0:
+      if not self.symbol_addresses:
         # The first symbol in text sections
         text_section_start = addr
         self.symbol_addresses.append(0)
@@ -374,9 +374,9 @@ class HeatmapGenerator(object):
 
   def _map_addr_to_symbol(self, addr):
     # Find out the symbol name
-    assert len(self.symbol_addresses) > 0
+    assert self.symbol_addresses
     index = bisect.bisect(self.symbol_addresses, addr)
-    assert index > 0 and index <= len(self.symbol_names), \
+    assert 0 < index <= len(self.symbol_names), \
     'Failed to find an index (%d) in the list (len=%d)' % (
         index, len(self.symbol_names))
     return self.symbol_names[index - 1]
@@ -387,7 +387,7 @@ class HeatmapGenerator(object):
       print(
           '----------------------------------------------------------', file=fp)
       print(
-          'Page Offset: %d MB, Count: %d' % (page_num / 1024 / 1024,
+          'Page Offset: %d MB, Count: %d' % (page_num // 1024 // 1024,
                                              sample_num),
           file=fp)
 
@@ -400,8 +400,8 @@ class HeatmapGenerator(object):
           if pid is None:
             # The sampling is not on Chrome
             continue
-          if addr / self.page_size != (
-              self.processes[pid].start_address + page_num) / self.page_size:
+          if addr // self.page_size != (
+              self.processes[pid].start_address + page_num) // self.page_size:
             # Sampling not in the current page
             continue
 
@@ -410,14 +410,14 @@ class HeatmapGenerator(object):
           assert name, 'Failed to find symbol name of addr %x' % addr
           symbol_counts[name] += 1
 
-      assert sum(symbol_counts.itervalues()) == sample_num, \
+      assert sum(symbol_counts.values()) == sample_num, \
       'Symbol name matching missing for some addresses: %d vs %d' % (
-          sum(symbol_counts.itervalues()), sample_num)
+          sum(symbol_counts.values()), sample_num)
 
       # Print out the symbol names sorted by the number of samples in
       # the page
       for name, count in sorted(
-          symbol_counts.iteritems(), key=lambda kv: kv[1], reverse=True):
+          symbol_counts.items(), key=lambda kv: kv[1], reverse=True):
         if count == 0:
           break
         print('> %s : %d' % (name, count), file=fp)
@@ -434,20 +434,19 @@ class HeatmapGenerator(object):
     # Read histogram from histo.txt
     hist = self._restore_histogram()
     # Sort the pages in histogram
-    sorted_hist = sorted(
-        hist.iteritems(), key=lambda value: value[1], reverse=True)
+    sorted_hist = sorted(hist.items(), key=lambda value: value[1], reverse=True)
 
     # Generate symbolizations
     self._read_symbols_from_binary(binary)
 
     # Write hottest pages
-    with open('addr2symbol.txt', 'w') as fp:
+    with open('addr2symbol.txt', 'w', encoding='utf-8') as fp:
       if self.hugepage:
         # Print hugepage region first
         print(
             'Hugepage top %d hot pages (%d MB - %d MB):' %
-            (top_n, self.hugepage.start / 1024 / 1024,
-             self.hugepage.end / 1024 / 1024),
+            (top_n, self.hugepage.start // 1024 // 1024,
+             self.hugepage.end // 1024 // 1024),
             file=fp)
         pages_to_print = [(k, v)
                           for k, v in sorted_hist
@@ -464,5 +463,5 @@ class HeatmapGenerator(object):
         self._print_symbols_in_hot_pages(fp, pages_to_print)
       else:
         # Print top_n hottest pages.
-        pages_to_print = [(k, v) for k, v in sorted_hist][:top_n]
+        pages_to_print = sorted_hist[:top_n]
         self._print_symbols_in_hot_pages(fp, pages_to_print)
diff --git a/heatmaps/heatmap_generator_test.py b/heatmaps/heatmap_generator_test.py
index 0c0bbfc8..5008c653 100755
--- a/heatmaps/heatmap_generator_test.py
+++ b/heatmaps/heatmap_generator_test.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright 2018 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -8,11 +8,12 @@
 
 from __future__ import division, print_function
 
-import mock
-import os
+import unittest.mock as mock
 import unittest
 
-import heatmap_generator
+import os
+
+from heatmaps import heatmap_generator
 
 
 def _write_perf_mmap(pid, tid, addr, size, fp):
diff --git a/llvm_extra/create_ebuild_file.py b/llvm_extra/create_ebuild_file.py
index 459e702a..058a270b 100755
--- a/llvm_extra/create_ebuild_file.py
+++ b/llvm_extra/create_ebuild_file.py
@@ -1,25 +1,21 @@
-#!/usr/bin/env python2
-
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
 # Copyright 2018 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-from __future__ import print_function
+"""Create llvm ebuild file.
 
-import os
-import sys
+This script takes an existing host llvm compiler ebuild and
+creates another build that should be installable in a prefixed location.
+The script patches a few lines in the llvm ebuild to make that happen.
 
-# This script takes an existing host llvm compiler ebuild and
-# creates another build that should be installable in a prefixed location.
-# The script patches a few lines in the llvm ebuild to make that happen.
-#
-# Since the script is based on the current llvm ebuild patterns,
-# it may need to be updated if those patterns change.
-#
-# This script should normally be invoked by the shell script
-# create_llvm_extra.sh .
+Since the script is based on the current llvm ebuild patterns,
+it may need to be updated if those patterns change.
+
+This script should normally be invoked by the shell script
+create_llvm_extra.sh .
 
-"""
 Below is an example of the expected diff of the newly generated ebuild with
 some explanation of the diffs.
 
@@ -40,8 +36,8 @@ diff -Nuar llvm-pre7.0_pre335547_p20180529.ebuild newly-created-file.ebuild
  # Change USE flags to match llvm ebuild installtion. To see the set of flags
  enabled in llvm compiler ebuild, run $ sudo emerge -pv llvm
 
--IUSE="debug +default-compiler-rt +default-libcxx doc libedit +libffi multitarget
-+IUSE="debug +default-compiler-rt +default-libcxx doc libedit +libffi +multitarget
+-IUSE="debug +default-compiler-rt +default-libcxx doc libedit +libffi"
++IUSE="debug +default-compiler-rt +default-libcxx doc libedit +libffi
         ncurses ocaml python llvm-next llvm-tot test xml video_cards_radeon"
 
  COMMON_DEPEND="
@@ -59,8 +55,8 @@ diff -Nuar llvm-pre7.0_pre335547_p20180529.ebuild newly-created-file.ebuild
 
         # Allow custom cmake build types (like 'Gentoo')
  # Convert use of PN to llvm in epatch commands.
--       epatch "${FILESDIR}"/cmake/${PN}-3.8-allow_custom_cmake_build_types.patch
-+       epatch "${FILESDIR}"/cmake/llvm-3.8-allow_custom_cmake_build_types.patch
+-       epatch "${FILESDIR}"/cmake/${PN}-3.8-allow_custom_cmake_build.patch
++       epatch "${FILESDIR}"/cmake/llvm-3.8-allow_custom_cmake_build.patch
 
         # crbug/591436
         epatch "${FILESDIR}"/clang-executable-detection.patch
@@ -94,6 +90,12 @@ diff -Nuar llvm-pre7.0_pre335547_p20180529.ebuild newly-created-file.ebuild
         # some users may find it useful
 """
 
+from __future__ import print_function
+
+import os
+import sys
+
+
 def process_line(line, text):
   # Process the line and append to the text we want to generate.
   # Check if line has any patterns that we want to handle.
@@ -103,7 +105,7 @@ def process_line(line, text):
     text.append(line)
   elif line.startswith('SLOT='):
     # Change SLOT to "${PV%%_p[[:digit:]]*}"
-    SLOT_STRING='SLOT="${PV%%_p[[:digit:]]*}"\n'
+    SLOT_STRING = 'SLOT="${PV%%_p[[:digit:]]*}"\n'
     text.append(SLOT_STRING)
   elif line.startswith('IUSE') and 'multitarget' in line:
     # Enable multitarget USE flag.
@@ -137,9 +139,9 @@ def process_line(line, text):
 
 def main():
   if len(sys.argv) != 3:
-     filename = os.path.basename(__file__)
-     print ('Usage: ', filename,' <input.ebuild> <output.ebuild>')
-     return 1
+    filename = os.path.basename(__file__)
+    print('Usage: ', filename, ' <input.ebuild> <output.ebuild>')
+    return 1
 
   text = []
   with open(sys.argv[1], 'r') as infile:
@@ -147,10 +149,10 @@ def main():
       process_line(line, text)
 
   with open(sys.argv[2], 'w') as outfile:
-    outfile.write("".join(text))
+    outfile.write(''.join(text))
 
   return 0
 
 
-if __name__== "__main__":
+if __name__ == '__main__':
   sys.exit(main())
diff --git a/llvm_tools/custom_script_example.py b/llvm_tools/custom_script_example.py
index 7e107ad8..38dff007 100755
--- a/llvm_tools/custom_script_example.py
+++ b/llvm_tools/custom_script_example.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright 2019 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
diff --git a/orderfile/post_process_orderfile.py b/orderfile/post_process_orderfile.py
index e24ab1cd..3db0b3b8 100755
--- a/orderfile/post_process_orderfile.py
+++ b/orderfile/post_process_orderfile.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright 2019 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -79,7 +79,7 @@ def main(argv):
   options = parser.parse_args(argv)
 
   if not os.path.exists(options.input_file):
-    sys.exit('Input orderfile doesn\'t exist.')
+    sys.exit("Input orderfile doesn\'t exist.")
 
   with open(options.input_file) as in_stream, \
   open(options.chrome_nm) as chrome_nm_stream, \
diff --git a/orderfile/post_process_orderfile_test.py b/orderfile/post_process_orderfile_test.py
index 2532b8b3..a5fb2c73 100755
--- a/orderfile/post_process_orderfile_test.py
+++ b/orderfile/post_process_orderfile_test.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright 2019 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -41,7 +41,7 @@ def _cleanup(files):
 class Tests(unittest.TestCase):
   """All of our tests for post_process_orderfile."""
 
-  #pylint: disable=protected-access
+  # pylint: disable=protected-access
   def test__parse_nm_output(self):
     temp_dir = tempfile.mkdtemp()
     self.addCleanup(_cleanup, [temp_dir])
diff --git a/pgo_tools/merge_profdata_and_upload.py b/pgo_tools/merge_profdata_and_upload.py
index dddc7f1e..ea95289b 100755
--- a/pgo_tools/merge_profdata_and_upload.py
+++ b/pgo_tools/merge_profdata_and_upload.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 # Copyright 2019 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -56,7 +56,8 @@ _LLVMMetadata = collections.namedtuple('_LLVMMetadata', ['head_sha'])
 def _get_gs_latest(remote_lastest):
   assert remote_lastest.startswith(_GS_PREFIX)
   try:
-    return subprocess.check_output(['gsutil', 'cat', remote_lastest])
+    return subprocess.check_output(['gsutil', 'cat', remote_lastest],
+                                   encoding='utf-8')
   except subprocess.CalledProcessError:
     raise RuntimeError('Lastest artifacts not found: %s' % remote_lastest)
 
@@ -142,7 +143,8 @@ def _tar_and_upload_profdata(profdata, name_suffix):
   print('Uploading tarball to gs.\nCMD: %s\n' % upload_cmd)
 
   # gsutil prints all status to stderr, oddly enough.
-  gs_output = subprocess.check_output(upload_cmd, stderr=subprocess.STDOUT)
+  gs_output = subprocess.check_output(
+      upload_cmd, stderr=subprocess.STDOUT, encoding='utf-8')
   print(gs_output)
 
   # gsutil exits successfully even if it uploaded nothing. It prints a summary
@@ -227,7 +229,7 @@ def main():
       for tryjob in args.tryjob:
         fetch_and_append_artifacts(tryjob)
 
-    assert heads, 'Didn\'t fetch anything?'
+    assert heads, "Didn't fetch anything?"
 
     def die_with_head_complaint(complaint):
       extra = ' (HEADs found: %s)' % sorted(heads)
@@ -239,7 +241,7 @@ def main():
         die_with_head_complaint(
             '%d LLVM HEADs were found, which is more than one. You probably '
             'want a consistent set of HEADs for a profile. If you know you '
-            'don\'t, please specify --llvm_hash, and note that *all* profiles '
+            "don't, please specify --llvm_hash, and note that *all* profiles "
             'will be merged into this final profile, regardless of their '
             'reported HEAD.' % len(heads))
       llvm_hash, = heads
@@ -247,7 +249,7 @@ def main():
     if llvm_hash not in heads:
       assert llvm_hash == args.llvm_hash
       die_with_head_complaint(
-          'HEAD %s wasn\'t found in any fetched artifacts.' % llvm_hash)
+          "HEAD %s wasn't found in any fetched artifacts." % llvm_hash)
 
     print('Using LLVM hash: %s' % llvm_hash)
 
diff --git a/run_tests_for.py b/run_tests_for.py
index cb8e6430..19f81722 100755
--- a/run_tests_for.py
+++ b/run_tests_for.py
@@ -37,6 +37,12 @@ import sys
 
 TestSpec = collections.namedtuple('TestSpec', ['directory', 'command'])
 
+# List of python scripts that are not test with relative path to
+# toolchain-utils.
+non_test_py_files = {
+    'debug_info_test/debug_info_test.py',
+}
+
 
 def _make_relative_to_toolchain_utils(toolchain_utils, path):
   """Cleans & makes a path relative to toolchain_utils.
@@ -52,13 +58,26 @@ def _make_relative_to_toolchain_utils(toolchain_utils, path):
   return result
 
 
-def _gather_python_tests_in(subdir):
+def _filter_python_tests(test_files, toolchain_utils):
+  """Returns all files that are real python tests."""
+  python_tests = []
+  for test_file in test_files:
+    rel_path = _make_relative_to_toolchain_utils(toolchain_utils, test_file)
+    if rel_path not in non_test_py_files:
+      python_tests.append(_python_test_to_spec(test_file))
+    else:
+      print('## %s ... NON_TEST_PY_FILE' % rel_path)
+  return python_tests
+
+
+def _gather_python_tests_in(rel_subdir, toolchain_utils):
   """Returns all files that appear to be Python tests in a given directory."""
+  subdir = os.path.join(toolchain_utils, rel_subdir)
   test_files = (
       os.path.join(subdir, file_name)
       for file_name in os.listdir(subdir)
       if file_name.endswith('_test.py') or file_name.endswith('_unittest.py'))
-  return [_python_test_to_spec(test_file) for test_file in test_files]
+  return _filter_python_tests(test_files, toolchain_utils)
 
 
 def _run_test(test_spec):
@@ -91,7 +110,7 @@ def _python_test_to_spec(test_file):
   return TestSpec(directory=test_directory, command=command)
 
 
-def _autodetect_python_tests_for(test_file):
+def _autodetect_python_tests_for(test_file, toolchain_utils):
   """Given a test file, detect if there may be related tests."""
   if not test_file.endswith('.py'):
     return []
@@ -103,8 +122,7 @@ def _autodetect_python_tests_for(test_file):
     base = test_file[:-3]
     candidates = (base + x for x in test_suffixes)
     test_files = (x for x in candidates if os.path.exists(x))
-
-  return [_python_test_to_spec(test_file) for test_file in test_files]
+  return _filter_python_tests(test_files, toolchain_utils)
 
 
 def _run_test_scripts(all_tests, show_successful_output=False):
@@ -195,7 +213,7 @@ def _find_forced_subdir_python_tests(test_paths, toolchain_utils):
 
   results = []
   for d in sorted(gather_test_dirs):
-    results += _gather_python_tests_in(os.path.join(toolchain_utils, d))
+    results += _gather_python_tests_in(d, toolchain_utils)
   return results
 
 
@@ -241,7 +259,7 @@ def main(argv):
   tests_to_run = _find_forced_subdir_python_tests(modified_files,
                                                   toolchain_utils)
   for f in modified_files:
-    tests_to_run += _autodetect_python_tests_for(f)
+    tests_to_run += _autodetect_python_tests_for(f, toolchain_utils)
   tests_to_run += _find_go_tests(modified_files)
 
   # TestSpecs have lists, so we can't use a set. We'd likely want to keep them
diff --git a/toolchain_utils_githooks/check-presubmit.py b/toolchain_utils_githooks/check-presubmit.py
index 2fea102a..fc6ec9fc 100755
--- a/toolchain_utils_githooks/check-presubmit.py
+++ b/toolchain_utils_githooks/check-presubmit.py
@@ -226,7 +226,7 @@ def check_cros_lint(toolchain_utils_root, thread_pool, files):
   # pylint+golint.
   def try_run_cros_lint(cros_binary):
     exit_code, output = run_command_unchecked(
-        [cros_binary, 'lint', '--'] + files,
+        [cros_binary, 'lint', '--py3', '--'] + files,
         toolchain_utils_root,
         env=fixed_env)