def test_arg_flaglistMalformedFlag(self):
        """
        A list of flags that contains a malformed flag raises
        L{imap4.IllegalClientResponse}.
        """
        self.assertRaises(imap4.IllegalClientResponse,
                          self.server.arg_flaglist, b"(first \x00)")
        self.assertRaises(imap4.IllegalClientResponse,
                          self.server.arg_flaglist, b"(first \x00second)")

        A list of flags that contains a malformed flag raises
        L{imap4.IllegalClientResponse}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/test/test_imap.py