Add a service class to the runner.
        There can only be one service class for a given service name.
        Service classes must be registered before calling start()

def add_service(self, cls):
        """ Add a service class to the runner.
        There can only be one service class for a given service name.
        Service classes must be registered before calling start()
        """
        service_name = get_service_name(cls)
        container = self.container_cls(cls, self.config)
        self.service_map[service_name] = container