def test_errors(self):
        """
        A subclass of L{XMLRPC} can override C{lookupProcedure} to raise
        L{NoSuchFunction} to indicate that a requested method is not available
        to be called, signalling a fault to the XML-RPC client.
        """
        self.createServer(TestLookupProcedure())
        d = self.proxy.callRemote("xxxx", "hello")
        d = self.assertFailure(d, xmlrpc.Fault)
        return d

        A subclass of L{XMLRPC} can override C{lookupProcedure} to raise
        L{NoSuchFunction} to indicate that a requested method is not available
        to be called, signalling a fault to the XML-RPC client.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_xmlrpc.py