"keystoneauth1.exceptions.catalog.EmptyCatalog: The service catalog is empty." in test_cinderclient_unsupported_v1

This just started failing today:

http://logs.openstack.org/18/417118/1/check/gate-nova-python27-db-ubuntu-xenial/0c0c8c1/console.html#_2017-01-05_17_52_16_199447

2017-01-05 17:52:16.199447 | nova.tests.unit.test_cinder.CinderV1TestCase.test_cinderclient_unsupported_v1
2017-01-05 17:52:16.199481 | -----------------------------------------------------------------------------
2017-01-05 17:52:16.199488 |
2017-01-05 17:52:16.199498 | Captured traceback:
2017-01-05 17:52:16.199510 | ~~~~~~~~~~~~~~~~~~~
2017-01-05 17:52:16.199525 | Traceback (most recent call last):
2017-01-05 17:52:16.199568 | File "/home/jenkins/workspace/gate-nova-python27-db-ubuntu-xenial/.tox/py27/local/lib/python2.7/site-packages/mock/mock.py", line 1305, in patched
2017-01-05 17:52:16.199585 | return func(*args, **keywargs)
2017-01-05 17:52:16.199612 | File "nova/tests/unit/test_cinder.py", line 134, in test_cinderclient_unsupported_v1
2017-01-05 17:52:16.199627 | cinder.cinderclient, ctxt)
2017-01-05 17:52:16.199684 | File "/home/jenkins/workspace/gate-nova-python27-db-ubuntu-xenial/.tox/py27/local/lib/python2.7/site-packages/testtools/testcase.py", line 485, in assertRaises
2017-01-05 17:52:16.199701 | self.assertThat(our_callable, matcher)
2017-01-05 17:52:16.199768 | File "/home/jenkins/workspace/gate-nova-python27-db-ubuntu-xenial/.tox/py27/local/lib/python2.7/site-packages/testtools/testcase.py", line 496, in assertThat
2017-01-05 17:52:16.199794 | mismatch_error = self._matchHelper(matchee, matcher, message, verbose)
2017-01-05 17:52:16.199839 | File "/home/jenkins/workspace/gate-nova-python27-db-ubuntu-xenial/.tox/py27/local/lib/python2.7/site-packages/testtools/testcase.py", line 547, in _matchHelper
2017-01-05 17:52:16.199854 | mismatch = matcher.match(matchee)
2017-01-05 17:52:16.199899 | File "/home/jenkins/workspace/gate-nova-python27-db-ubuntu-xenial/.tox/py27/local/lib/python2.7/site-packages/testtools/matchers/_exception.py", line 108, in match
2017-01-05 17:52:16.199919 | mismatch = self.exception_matcher.match(exc_info)
2017-01-05 17:52:16.199975 | File "/home/jenkins/workspace/gate-nova-python27-db-ubuntu-xenial/.tox/py27/local/lib/python2.7/site-packages/testtools/matchers/_higherorder.py", line 62, in match
2017-01-05 17:52:16.199992 | mismatch = matcher.match(matchee)
2017-01-05 17:52:16.200033 | File "/home/jenkins/workspace/gate-nova-python27-db-ubuntu-xenial/.tox/py27/local/lib/python2.7/site-packages/testtools/testcase.py", line 475, in match
2017-01-05 17:52:16.200045 | reraise(*matchee)
2017-01-05 17:52:16.200088 | File "/home/jenkins/workspace/gate-nova-python27-db-ubuntu-xenial/.tox/py27/local/lib/python2.7/site-packages/testtools/matchers/_exception.py", line 101, in match
2017-01-05 17:52:16.200100 | result = matchee()
2017-01-05 17:52:16.200142 | File "/home/jenkins/workspace/gate-nova-python27-db-ubuntu-xenial/.tox/py27/local/lib/python2.7/site-packages/testtools/testcase.py", line 1049, in __call__
2017-01-05 17:52:16.200162 | return self._callable_object(*self._args, **self._kwargs)
2017-01-05 17:52:16.200181 | File "nova/volume/cinder.py", line 80, in cinderclient
2017-01-05 17:52:16.200203 | url = _SESSION.get_endpoint(auth, **service_parameters)
2017-01-05 17:52:16.200247 | File "/home/jenkins/workspace/gate-nova-python27-db-ubuntu-xenial/.tox/py27/local/lib/python2.7/site-packages/keystoneauth1/session.py", line 808, in get_endpoint
2017-01-05 17:52:16.200263 | return auth.get_endpoint(self, **kwargs)
2017-01-05 17:52:16.200281 | File "nova/context.py", line 61, in get_endpoint
2017-01-05 17:52:16.200294 | region_name=region_name)
2017-01-05 17:52:16.200391 | File "/home/jenkins/workspace/gate-nova-python27-db-ubuntu-xenial/.tox/py27/local/lib/python2.7/site-packages/positional/__init__.py", line 101, in inner
2017-01-05 17:52:16.200420 | return wrapped(*args, **kwargs)
2017-01-05 17:52:16.200467 | File "/home/jenkins/workspace/gate-nova-python27-db-ubuntu-xenial/.tox/py27/local/lib/python2.7/site-packages/keystoneauth1/access/service_catalog.py", line 190, in url_for
2017-01-05 17:52:16.200490 | raise exceptions.EmptyCatalog('The service catalog is empty.')
2017-01-05 17:52:16.200527 | keystoneauth1.exceptions.catalog.EmptyCatalog: The service catalog is empty.

It's a race in a test introduced in https://review.openstack.org/#/c/409904/.

I suspect it's a race in a global mock.