stable/yoga gate blocker: failures in py39 unit tests

All jobs in nova.tests.unit.cmd.test_manage.DbCommandsTestCase, as well as test_nova.tests.unit.cmd.test_manage.UtilitiesTestCase.test_format_dict.

One specific example:
```
ft2.1: nova.tests.unit.cmd.test_manage.UtilitiesTestCase.test_format_dicttesttools.testresult.real._StringException: pythonlogging:'': {{{
2022-09-01 17:37:16,772 WARNING [oslo_policy.policy] JSON formatted policy_file support is deprecated since Victoria release. You need to use YAML format which will be default in future. You can use ``oslopolicy-convert-json-to-yaml`` tool to convert existing JSON-formatted policy file to YAML-formatted in backward compatible way: https://docs.openstack.org/oslo.policy/latest/cli/oslopolicy-convert-json-to-yaml.html.
2022-09-01 17:37:16,773 WARNING [oslo_policy.policy] JSON formatted policy_file support is deprecated since Victoria release. You need to use YAML format which will be default in future. You can use ``oslopolicy-convert-json-to-yaml`` tool to convert existing JSON-formatted policy file to YAML-formatted in backward compatible way: https://docs.openstack.org/oslo.policy/latest/cli/oslopolicy-convert-json-to-yaml.html.
2022-09-01 17:37:16,774 WARNING [oslo_policy.policy] Policy Rules ['os_compute_api:extensions', 'os_compute_api:os-floating-ip-pools', 'os_compute_api:os-quota-sets:defaults', 'os_compute_api:os-availability-zone:list', 'os_compute_api:limits', 'project_admin_api', 'project_member_api', 'project_reader_api', 'project_reader_or_admin', 'os_compute_api:limits:other_project', 'os_compute_api:os-lock-server:unlock:unlock_override', 'os_compute_api:servers:create:zero_disk_flavor', 'compute:servers:resize:cross_cell'] specified in policy files are the same as the defaults provided by the service. You can remove these rules from policy files which will make maintenance easier. You can detect these redundant rules by ``oslopolicy-list-redundant`` tool also.
}}}

Traceback (most recent call last):
  File "/home/zuul/src/opendev.org/openstack/nova/nova/tests/unit/cmd/test_manage.py", line 55, in test_format_dict
    self.assertEqual(
  File "/home/zuul/src/opendev.org/openstack/nova/.tox/py39/lib/python3.9/site-packages/testtools/testcase.py", line 393, in assertEqual
    self.assertThat(observed, matcher, message)
  File "/home/zuul/src/opendev.org/openstack/nova/.tox/py39/lib/python3.9/site-packages/testtools/testcase.py", line 480, in assertThat
    raise mismatch_error
testtools.matchers._impl.MismatchError: !=:
reference = '''\
+----------+----------------------+
| Property | Value |
+----------+----------------------+
| bing | bat |
| foo | bar |
| test | {'a nested': 'dict'} |
| wow | a multiline |
| | string |
+----------+----------------------+'''
actual = '''\
+----------+----------------------+
| Property | Value |
+----------+----------------------+
| bing | bat |
| foo | bar |
| test | {'a nested': 'dict'} |
| wow | a multiline |
| | string |
+----------+----------------------+'''

```

This is failing on at least two different changes that are completely unrelated and are unlikely to be causing these failures:
- https://review.opendev.org/c/openstack/nova/+/855025
- https://review.opendev.org/c/openstack/nova/+/854257

I was unable to create an opensearch query to find all these failures, but https://tinyurl.com/mr3pjzyn catches related failures in cross-nova-py38

I was able to reproduce the failure in test_format_dict locally, by downloading 854257 and running tox -e py39. Output from that reproduction is:

```
nova.tests.unit.cmd.test_manage.UtilitiesTestCase.test_format_dict
------------------------------------------------------------------

Captured traceback:
~~~~~~~~~~~~~~~~~~~
    Traceback (most recent call last):

      File "/home/jay/dev/nova/nova/tests/unit/cmd/test_manage.py", line 55, in test_format_dict
    self.assertEqual(

      File "/home/jay/dev/nova/.tox/py39/lib/python3.9/site-packages/testtools/testcase.py", line 393, in assertEqual
    self.assertThat(observed, matcher, message)

      File "/home/jay/dev/nova/.tox/py39/lib/python3.9/site-packages/testtools/testcase.py", line 480, in assertThat
    raise mismatch_error

    testtools.matchers._impl.MismatchError: !=:
reference = '''\
+----------+----------------------+
| Property | Value |
+----------+----------------------+
| bing | bat |
| foo | bar |
| test | {'a nested': 'dict'} |
| wow | a multiline |
| | string |
+----------+----------------------+'''
actual = '''\
+----------+----------------------+
| Property | Value |
+----------+----------------------+
| bing | bat |
| foo | bar |
| test | {'a nested': 'dict'} |
| wow | a multiline |
| | string |
+----------+----------------------+'''
```