utils: update CalledProcessError output python compat logic

We can leverage the parent's stderr setting now, but we can't get rid
of the output/stdout cleanup since Python 3.6 still does this.

Bug: None
Test: unittests
Change-Id: I52f2658d95aa4fdd08deabf68ad03599cb5b472a

2 files changed, 32 insertions, 7 deletions

diff --git a/rh/utils.py b/rh/utils.py
index 86ff691..157e31b 100644
--- a/rh/utils.py
+++ b/rh/utils.py
@@ -84,17 +84,26 @@ class CalledProcessError(subprocess.CalledProcessError):
     """
 
     def __init__(self, returncode, cmd, stdout=None, stderr=None, msg=None):
-        super().__init__(returncode, cmd, stdout)
-        # The parent class will set |output|, so delete it.
+        super().__init__(returncode, cmd, stdout, stderr=stderr)
+
+        # The parent class will set |output|, so delete it. If Python ever drops
+        # this output/stdout compat logic, we can drop this to match.
         del self.output
-        # TODO(vapier): When we're Python 3-only, delete this assignment as the
-        # parent handles it for us.
-        self.stdout = stdout
-        # TODO(vapier): When we're Python 3-only, move stderr to the init above.
-        self.stderr = stderr
+        self._stdout = stdout
+
         self.msg = msg
 
     @property
+    def stdout(self):
+        """Override parent's usage of .output"""
+        return self._stdout
+
+    @stdout.setter
+    def stdout(self, value):
+        """Override parent's usage of .output"""
+        self._stdout = value
+
+    @property
     def cmdstr(self):
         """Return self.cmd as a well shell-quoted string for debugging."""
         return '' if self.cmd is None else rh.shell.cmd_to_str(self.cmd)
diff --git a/rh/utils_unittest.py b/rh/utils_unittest.py
index 277abff..bf720a7 100755
--- a/rh/utils_unittest.py
+++ b/rh/utils_unittest.py
@@ -117,6 +117,22 @@ class CalledProcessErrorTests(unittest.TestCase):
         err = rh.utils.CalledProcessError(0, ['mycmd'])
         self.assertNotEqual('', repr(err))
 
+    def test_output(self):
+        """Make sure .output is removed and .stdout works."""
+        e = rh.utils.CalledProcessError(
+            0, ['true'], stdout='STDOUT', stderr='STDERR')
+        with self.assertRaises(AttributeError):
+            assert e.output is None
+        assert e.stdout == 'STDOUT'
+        assert e.stderr == 'STDERR'
+
+        e.stdout = 'STDout'
+        e.stderr = 'STDerr'
+        with self.assertRaises(AttributeError):
+            assert e.output is None
+        assert e.stdout == 'STDout'
+        assert e.stderr == 'STDerr'
+
 
 class RunCommandTests(unittest.TestCase):
     """Verify behavior of run helper."""