Close a room.

        This function removes all the clients from the given room.

        :param room: Room name.
        :param namespace: The Socket.IO namespace for the event. If this
                          argument is omitted the default namespace is used.

        Note: this method is a coroutine.

async def close_room(self, room, namespace=None):
        """Close a room.

        This function removes all the clients from the given room.

        :param room: Room name.
        :param namespace: The Socket.IO namespace for the event. If this
                          argument is omitted the default namespace is used.

        Note: this method is a coroutine.
        """
        namespace = namespace or '/'
        self.logger.info('room %s is closing [%s]', room, namespace)
        await self.manager.close_room(room, namespace)