def testPassphraseError(self):
        """
        Calling save() with a passphrase is an error.
        """
        p = sob.Persistant(None, 'object')
        self.assertRaises(
            TypeError, p.save, 'filename.pickle', passphrase='abc')

        Calling save() with a passphrase is an error.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_sob.py