def test_tracebackFromExceptionInPython3(self):
        """
        If a L{failure.Failure} is constructed with an exception but no
        traceback in Python 3, the traceback will be extracted from the
        exception's C{__traceback__} attribute.
        """
        try:
            1/0
        except:
            klass, exception, tb = sys.exc_info()
        f = failure.Failure(exception)
        self.assertIs(f.tb, tb)

        If a L{failure.Failure} is constructed with an exception but no
        traceback in Python 3, the traceback will be extracted from the
        exception's C{__traceback__} attribute.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_failure.py