def _on_call_service_msg(self, msg):
        """
        Stub service handler. Start a thread to import the mitogen.service
        implementation from, and deliver the message to the newly constructed
        pool. This must be done as CALL_SERVICE for e.g. PushFileService may
        race with a CALL_FUNCTION blocking the main thread waiting for a result
        from that service.
        """
        if not msg.is_dead:
            th = threading.Thread(target=self._service_stub_main, args=(msg,))
            th.start()
Stub service handler. Start a thread to import the mitogen.service
        implementation from, and deliver the message to the newly constructed
        pool. This must be done as CALL_SERVICE for e.g. PushFileService may
        race with a CALL_FUNCTION blocking the main thread waiting for a result
        from that service.