pylint: handle missing pylint better

If you don't have pylint installed, trying to run pylint will result in
confusuing output:

Traceback (most recent call last):
  File "./tools/pylint.py", line 69, in <module>
    sys.exit(main(sys.argv[1:]))
  File "./tools/pylint.py", line 65, in main
    os.execvp(cmd[0], cmd)
  File "/usr/lib/python2.7/os.py", line 346, in execvp
    _execvpe(file, args)
  File "/usr/lib/python2.7/os.py", line 382, in _execvpe
    func(fullname, *argrest)
OSError: [Errno 2] No such file or directory

Rather than make people guess that they need to install pylint, catch
this error and display something more user friendly:

pylint.py: unable to run `pylint`: [Errno 2] No such file or directory
pylint.py: Try installing pylint: sudo apt-get install pylint

Bug: None
Test: `./tools/pylint.py tools/cpplint.py --executable-path asdf` no longer barfs
Change-Id: I7a259e2d950d66855c0dea367e035fe6adc4ce93

1 files changed, 14 insertions, 1 deletions

diff --git a/tools/pylint.py b/tools/pylint.py
index 6091c1d..1c8e6f7 100755
--- a/tools/pylint.py
+++ b/tools/pylint.py
@@ -19,12 +19,15 @@
 from __future__ import print_function
 
 import argparse
+import errno
 import os
 import sys
 
+
 DEFAULT_PYLINTRC_PATH = os.path.join(
     os.path.dirname(os.path.realpath(__file__)), 'pylintrc')
 
+
 def get_parser():
     """Return a command line parser."""
     parser = argparse.ArgumentParser(description=__doc__)
@@ -62,7 +65,17 @@ def main(argv):
     if opts.init_hook:
         cmd += ['--init-hook', opts.init_hook]
 
-    os.execvp(cmd[0], cmd)
+    try:
+        os.execvp(cmd[0], cmd)
+    except OSError as e:
+        if e.errno == errno.ENOENT:
+            print('%s: unable to run `%s`: %s' % (__file__, cmd[0], e),
+                  file=sys.stderr)
+            print('%s: Try installing pylint: sudo apt-get install pylint' %
+                  (__file__,), file=sys.stderr)
+            return 1
+        else:
+            raise
 
 
 if __name__ == '__main__':