def test_regularFailure(self):
        """
        If startDebugMode() is called, calling Failure() will first call
        pdb.post_mortem with the traceback.
        """
        try:
            1/0
        except:
            typ, exc, tb = sys.exc_info()
            f = failure.Failure()
        self.assertEqual(self.result, [tb])
        self.assertFalse(f.captureVars)

        If startDebugMode() is called, calling Failure() will first call
        pdb.post_mortem with the traceback.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_failure.py