def test_add_already_added(self):
        prio_set_list = event._PrioritizedSetList()
        obj = object()
        prio_set_list.add(0, obj)

        with pytest.raises(ValueError) as excinfo:
            prio_set_list.add(0, obj)
        excinfo.match(r"has already been added")

        with pytest.raises(ValueError) as excinfo:
            prio_set_list.add(1, obj)
        excinfo.match(r"has already been added")
async def echo_client(loop, client):
    try:
        client.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
    except (OSError, NameError):
        pass

    with client:
        while True:
            data = await loop.sock_recv(client, 1000000)
            if not data:
                break
            await loop.sock_sendall(client, data)
    if PRINT:
        print('Connection closed')