DeprecationWarning: Please use assertRaisesRegex instead.

[mtelka]

pydiffx/tests/test_reader.py: 10 warnings
pydiffx/tests/test_utils_unified_diffs.py: 7 warnings
pydiffx/tests/test_dom_objects.py: 22 warnings
pydiffx/tests/test_writer.py: 27 warnings
pydiffx/tests/test_utils_text.py: 2 warnings
  $(@D)/pydiffx/tests/testcases.py:68: DeprecationWarning: Please use assertRaisesRegex instead.
    with self.assertRaisesRegexp(exception, re.escape(message)):

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html

[jonathanspw]

This causes failures to build on Python 3.12.

See https://bugzilla.redhat.com/show_bug.cgi?id=2175200