def test_cleanFailureRemovesTracebackInPython3(self):
        """
        L{failure.Failure.cleanFailure} sets the C{__traceback__} attribute of
        the exception to L{None} in Python 3.
        """
        f = getDivisionFailure()
        self.assertIsNotNone(f.tb)
        self.assertIs(f.value.__traceback__, f.tb)
        f.cleanFailure()
        self.assertIsNone(f.value.__traceback__)

        L{failure.Failure.cleanFailure} sets the C{__traceback__} attribute of
        the exception to L{None} in Python 3.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_failure.py