test_distributed_port_binding_deleted_by_port_deletion failed due to warnings during port binding delete

[Ihar Hrachyshka]

http://logs.openstack.org/56/534456/1/check/openstack-tox-py35/151aefe/testr_results.html.gz (Queens)

ft1.6: neutron.tests.unit.plugins.ml2.test_db.Ml2DvrDBTestCase.test_distributed_port_binding_deleted_by_port_deletion_StringException: Traceback (most recent call last):
  File "/home/zuul/src/git.openstack.org/openstack/neutron/neutron/tests/base.py", line 132, in func
    return f(self, *args, **kwargs)
  File "/home/zuul/src/git.openstack.org/openstack/neutron/neutron/tests/unit/plugins/ml2/test_db.py", line 438, in test_distributed_port_binding_deleted_by_port_deletion
    self.assertEqual([], warning_list)
  File "/home/zuul/src/git.openstack.org/openstack/neutron/.tox/py35/lib/python3.5/site-packages/testtools/testcase.py", line 411, in assertEqual
    self.assertThat(observed, matcher, message)
  File "/home/zuul/src/git.openstack.org/openstack/neutron/.tox/py35/lib/python3.5/site-packages/testtools/testcase.py", line 498, in assertThat
    raise mismatch_error
testtools.matchers._impl.MismatchError: !=:
reference = []
actual = [<warnings.WarningMessage object at 0x7ff014f870f0>,
 <warnings.WarningMessage object at 0x7ff012266160>]

It's not clear which warnings those objects are (we may extend the test to expose those on failure).

The failure itself may be related to OVO adoption for port bindings that landed lately: https://review.openstack.org/407868

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.openstack.org/535980

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/535980
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=b94b97617d564c4751a7f981b49f37ba05455217
Submitter: Zuul
Branch: master

commit b94b97617d564c4751a7f981b49f37ba05455217
Author: Ihar Hrachyshka <email address hidden>
Date: Fri Jan 19 14:19:39 2018 -0800

    Log warnings when test fails because of them

    When the test case fails, it's useful to see which warnings triggered
    the failure.

    Change-Id: Ia4150a06989ba253ffed0c0995e1023ca1ed42a0
    Related-Bug: #1744394