def clean_semver(cls, version_spec):
        return re.sub(r"([<>=~])\s+?v?", "\\1", version_spec, re.IGNORECASE)
def test_base_class_populate_old_value_of_change_raises_error(self):
        with self.assertRaisesRegex(
            NotImplementedError,
            'Subclasses of BaseSuggestion should implement'
            ' populate_old_value_of_change.'):
            self.base_suggestion.populate_old_value_of_change()