def test_notLookupMissingByValue(self):
        """
        L{Values.lookupByValue} raises L{ValueError} when called with a value
        with which no constant is associated.
        """
        self.assertRaises(ValueError, self.STATUS.lookupByValue, "OK")
        self.assertRaises(ValueError, self.STATUS.lookupByValue, 200)
        self.assertRaises(ValueError, self.STATUS.lookupByValue, "200.1")

        L{Values.lookupByValue} raises L{ValueError} when called with a value
        with which no constant is associated.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/test/test_constants.py