Intermittent "expected string or buffer" exception in py3 jobs

[Ben Nemec]

We've seen this at least a couple of times in the gate, although to my knowledge no one has been able to reproduce locally. In the exception propagation test tests.test_excutils.SaveAndReraiseTest.test_save_and_reraise_exception_dropped there is another exception being raised with the message in the title that is breaking the test.

Example traceback:

2015-03-18 17:35:23.220 | Traceback (most recent call last):
2015-03-18 17:35:23.220 | File "/home/jenkins/workspace/gate-oslo.utils-python34/.tox/py34/lib/python3.4/site-packages/mock.py", line 1201, in patched
2015-03-18 17:35:23.220 | return func(*args, **keywargs)
2015-03-18 17:35:23.220 | File "/home/jenkins/workspace/gate-oslo.utils-python34/tests/test_excutils.py", line 57, in test_save_and_reraise_exception_dropped
2015-03-18 17:35:23.220 | self.assertEqual(str(e), msg)
2015-03-18 17:35:23.220 | File "/home/jenkins/workspace/gate-oslo.utils-python34/.tox/py34/lib/python3.4/site-packages/testtools/testcase.py", line 350, in assertEqual
2015-03-18 17:35:23.221 | self.assertThat(observed, matcher, message)
2015-03-18 17:35:23.221 | File "/home/jenkins/workspace/gate-oslo.utils-python34/.tox/py34/lib/python3.4/site-packages/testtools/testcase.py", line 435, in assertThat
2015-03-18 17:35:23.221 | raise mismatch_error
2015-03-18 17:35:23.221 | testtools.matchers._impl.MismatchError: 'expected string or buffer' != 'second exception'

[Victor Stinner (vstinner)]

Bash script to reproduce the issue:

set -e -x
find -name "*.pyc" -delete
find -name "__pycache__"|xargs rm -rf
rm -rf .testrepository
tox -e py34
tox -e py27
rm -rf .testrepository
tox -e py34

The sporadic failure may be related to the order of imports?

[Doug Hellmann (doug-hellmann)]

On a random run on my system I got a more detailed traceback: http://paste.openstack.org/show/195344/

[Victor Stinner (vstinner)]

Much shorter script to reproduce the bug:

python -m testtools.run oslo_utils.tests.test_netutils.TestIsIPv6Enabled.test_disabled tests.test_excutils.SaveAndReraiseTest.test_save_and_reraise_exception_dropped

I'm working a fix. It's a bug in test_netutils.TestIsIPv6Enabled which never stops a mock.

[Ben Nemec (bnemec)]

Should be fixed by: https://review.openstack.org/#/c/166835/