'Locate a callable to invoke when executing the named command.
@param name: the normalized name (from the wire) of the command.
@type name: C{bytes}
@return: a 1-argument function that takes a Box and returns a box or a
Deferred which fires a Box, for handling the command identified by the
given name, or None, if no appropriate responder can be found.'

def locateResponder(self, name):

    cd = self._commandDispatch
    if (name in cd):
        (commandClass, responderFunc) = cd[name]
        if _PY3:
            responderMethod = types.MethodType(responderFunc, self)
        else:
            responderMethod = types.MethodType(responderFunc, self, self.__class__)
        return self._wrapWithSerialization(responderMethod, commandClass)
