Heroku在我的discord机器人里找不到Pycal

Question

2020-07-25T01:12:27.370500+00:00 app[worker.1]: Ignoring exception in on_voice_state_update
2020-07-25T01:12:27.371718+00:00 app[worker.1]: Traceback (most recent call last):
2020-07-25T01:12:27.371770+00:00 app[worker.1]:   File "/app/.heroku/python/lib/python3.6/site-packages/discord/client.py", line 312, in _run_event
2020-07-25T01:12:27.371771+00:00 app[worker.1]:     await coro(*args, **kwargs)
2020-07-25T01:12:27.371774+00:00 app[worker.1]:   File "bot.py", line 63, in on_voice_state_update
2020-07-25T01:12:27.371774+00:00 app[worker.1]:     voice = await channel.connect()
2020-07-25T01:12:27.371776+00:00 app[worker.1]:   File "/app/.heroku/python/lib/python3.6/site-packages/discord/abc.py", line 1076, in connect
2020-07-25T01:12:27.371777+00:00 app[worker.1]:     voice = VoiceClient(state=state, timeout=timeout, channel=self)
2020-07-25T01:12:27.371794+00:00 app[worker.1]:   File "/app/.heroku/python/lib/python3.6/site-packages/discord/voice_client.py", line 91, in __init__
2020-07-25T01:12:27.371795+00:00 app[worker.1]:     raise RuntimeError("PyNaCl library needed in order to use voice")
2020-07-25T01:12:27.371828+00:00 app[worker.1]: RuntimeError: PyNaCl library needed in order to use voice

我的discord机器人工作正常，当我用编辑器启动它时，它可以做音乐。但当heroku尝试这样做时，我得到了这个错误。我该怎么办？我通过pip安装了PyNaCl。我不知道如何将它添加到我的代码中，因为我的代码在没有pynacl的情况下运行良好，并且使用pynacl时运行良好。我无法在代码中导入它（找不到模块）。我不知道那是什么