python3.9.6 unit test races

To recreate:

lxc launch ubuntu-daily:impish impish
lxc exec impish /bin/bash
# install tox / deps
# clone manila
tox -e py39
...

The specific failure seem to be a bit nondeterministic, but the following are the ones I've seen so far

======================================================================
FAIL: manila.tests.db.sqlalchemy.test_api.ShareAccessDatabaseAPITestCase.test_share_access_get_all_for_share_2_3
manila.tests.db.sqlalchemy.test_api.ShareAccessDatabaseAPITestCase.test_share_access_get_all_for_share_2_3
----------------------------------------------------------------------
testtools.testresult.real._StringException: Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/ddt.py", line 182, in wrapper
    return func(self, *args, **kwargs)
  File "/<<BUILDDIR>>/manila-12.0.0+git2021061112.9974f047/manila/tests/db/sqlalchemy/test_api.py", line 114, in test_share_access_get_all_for_share
    self.assertEqual(rule_ids, result_ids)
  File "/usr/lib/python3/dist-packages/testtools/testcase.py", line 415, in assertEqual
    self.assertThat(observed, matcher, message)
  File "/usr/lib/python3/dist-packages/testtools/testcase.py", line 502, in assertThat
    raise mismatch_error
testtools.matchers._impl.MismatchError: !=:
reference = ['d41b6b74-eb49-48b2-a15b-f2c7ab9b7ff8',
 'c9ec4198-9a3c-4a0f-85ea-7f6b4c60c0b2',
 '6956add8-9827-4522-b08a-bd00eec2a117']
actual = ['6956add8-9827-4522-b08a-bd00eec2a117',
 'c9ec4198-9a3c-4a0f-85ea-7f6b4c60c0b2',
 'd41b6b74-eb49-48b2-a15b-f2c7ab9b7ff8']

======================================================================
FAIL: manila.tests.db.sqlalchemy.test_api.ShareAccessDatabaseAPITestCase.test_share_access_get_all_for_share_with_metadata
manila.tests.db.sqlalchemy.test_api.ShareAccessDatabaseAPITestCase.test_share_access_get_all_for_share_with_metadata
----------------------------------------------------------------------
testtools.testresult.real._StringException: Traceback (most recent call last):
  File "/<<BUILDDIR>>/manila-12.0.0+git2021061112.9974f047/manila/tests/db/sqlalchemy/test_api.py", line 309, in test_share_access_get_all_for_share_with_metadata
    self.assertEqual(rule_ids, result_ids)
  File "/usr/lib/python3/dist-packages/testtools/testcase.py", line 415, in assertEqual
    self.assertThat(observed, matcher, message)
  File "/usr/lib/python3/dist-packages/testtools/testcase.py", line 502, in assertThat
    raise mismatch_error
testtools.matchers._impl.MismatchError: !=:
reference = ['72f9fba0-38d0-486d-88fc-b23cde118e50',
 'b32e1184-b27c-419d-9ad8-15cb9b907ccb',
 '19d55fa1-c5c1-47ea-b8ae-e749a451c950']
actual = ['19d55fa1-c5c1-47ea-b8ae-e749a451c950',
 '72f9fba0-38d0-486d-88fc-b23cde118e50',
 'b32e1184-b27c-419d-9ad8-15cb9b907ccb']