Python: Fix missing assertRaisesRegexp method in Python 3.12

[Mingun]

Some manual tests uses assertRaisesRegex method, that's named assertRaisesRegexp in Python 2 (and that name is used). If we want to continue support Python 2, then we should use the fix, described in this SO answer:

# Add that code somewhere in the test
if not hasattr(unittest.TestCase, 'assertRaisesRegex'):
    setattr(unittest.TestCase, 'assertRaisesRegex', unittest.TestCase.assertRaisesRegexp)