How to use the aiozmq._test_util.find_unused_port function in aiozmq

def make_rpc_pair(self):
        port = find_unused_port()

        @asyncio.coroutine
        def create():
            server = yield from aiozmq.rpc.serve_rpc(
                MyHandler(),
                bind='tcp://127.0.0.1:{}'.format(port),
                loop=self.loop)

            client = yield from aiozmq.rpc.connect_rpc(
                connect='tcp://127.0.0.1:{}'.format(port),
                loop=self.loop)
            return client, server

        self.client, self.server = self.loop.run_until_complete(create())

        return self.client, self.server