import asyncio


async def main():
    loop = asyncio.get_running_loop()
    errors = []
    loop.set_exception_handler(lambda _, ctx: errors.append(ctx))

    connected = loop.create_future()

    def callback(reader, writer):
        connected.set_result(writer.transport)
        raise RuntimeError("boom")

    server = await asyncio.start_server(callback, "127.0.0.1", 0)
    _, client = await asyncio.open_connection(
        *server.sockets[0].getsockname()
    )

    transport = await connected
    print(len(errors), transport.is_closing())  # 1 False

    transport.close()
    client.close()
    server.close()
    await server.wait_closed()


asyncio.run(main())