Failing hacking tests when building Rocky Debian package under Python 3.7

[Thomas Goirand]

Building the Nova 18.0.0 package in Sid (ie: Python 3.7), I get the below unit test failure with hacking tests:

======================================================================
FAIL: nova.tests.unit.test_hacking.HackingTestCase.test_check_doubled_words
nova.tests.unit.test_hacking.HackingTestCase.test_check_doubled_words
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_StringException: Traceback (most recent call last):
  File "/<<PKGBUILDDIR>>/nova/tests/unit/test_hacking.py", line 586, in test_check_doubled_words
    expected_errors=errors)
  File "/<<PKGBUILDDIR>>/nova/tests/unit/test_hacking.py", line 293, in _assert_has_errors
    self.assertEqual(expected_errors or [], actual_errors)
  File "/usr/lib/python3/dist-packages/testtools/testcase.py", line 411, in assertEqual
    self.assertThat(observed, matcher, message)
  File "/usr/lib/python3/dist-packages/testtools/testcase.py", line 498, in assertThat
    raise mismatch_error
testtools.matchers._impl.MismatchError: [(1, 0, 'N343')] != []