def test_hiddenUserError(self):
        """
        'HIDDEN-USER' error should map to the L{ident.HiddenUser} exception.
        """
        d = defer.Deferred()
        self.client.queries.append((d, 567, 789))
        self.client.lineReceived('567, 789 : ERROR : HIDDEN-USER')
        return self.assertFailure(d, ident.HiddenUser)

        'HIDDEN-USER' error should map to the L{ident.HiddenUser} exception.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_ident.py