Fix pylint errors in cbuildbot_unittest and cros_test_lib.
Fix pylint errors in cbuildbot_unittest and cros_test_lib.

BUG=none
TEST=pylint
TEST=All unit tests.

Change-Id: I38f622ce8b86542b4c29ced578e091262eb4d521
Reviewed-on: https://chromium-review.googlesource.com/178791
Tested-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>
Reviewed-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Reviewed-by: Yu-Ju Hong <52dc720c411f8e2156e608c1a8b894a917489667@chromium.org>
Commit-Queue: Colby Ranger <af08ec4699bcb1aef5f82db31dfd07cae565c495@google.com>

bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite