The exception message was not being printed. There is no need to have a
custom field for the exception message. Removing it fixes the problem.

Added a test to ensure the message is correct. Before the change this
test would have failed.
Merge pull request #115 from edx/pylintrc_fix

The exception message was not being printed.
Diff-quality should not raise an exception due to pylint internal warnings.

Pylint may pipe output to stderr but still complete and exit
with a exit code of 0. The pylint report is still valid and
consumable by diff-quality. (A good example of this is a deprecation
warning due to pylintrc configuration.)
Merge pull request #116 from benpatterson/benp/pylint-handle-warnings

Diff-quality should not fail on pylint warnings.
Version 0.6.1
Add failing test. Marked it as an expected failure so the build does not break