python - discord.errors.Forbidden: 403 FORBIDDEN (error code: 50013): Missing Permissions

Question

I've recently created a bot which is only allowed to send messages and read message history. In my own servers, the bot seemed to work flawlessly, but a certain user tried using the bot on his own server and the error discord.errors.Forbidden: 403 FORBIDDEN (error code: 50013): Missing Permissions popped up.

await message.channel.send(file=discord.File(io.BytesIO(meme), filename="meme.png"))

The line above is what's causing the error. I'm thinking that I need the 'Attach Files' permission, but for some reason it works without it on my testing servers.

Full traceback:

Traceback (most recent call last):
  File "/home/nemplayer/.local/lib/python3.7/site-packages/discord/client.py", line 270, in _run_event
    await coro(*args, **kwargs)
  File "bot/bot.py", line 78, in on_message
    await message.channel.send(file=discord.File(io.BytesIO(meme), filename="meme.png"))
  File "/home/nemplayer/.local/lib/python3.7/site-packages/discord/abc.py", line 806, in send
    content=content, tts=tts, embed=embed, nonce=nonce)
  File "/home/nemplayer/.local/lib/python3.7/site-packages/discord/http.py", line 218, in request
    raise Forbidden(r, data)
discord.errors.Forbidden: 403 FORBIDDEN (error code: 50013): Missing Permissions

Answer 1

As you said, error code: 50013 means that you don't have permission to perform that action.

ATTACH_FILES is not the only permission you must have, you may also need SEND_MESSAGES and VIEW_CHANNEL as they are "Implicit Permissions", check if you have them too.