我的代码偶尔会在使用此命令时出现 400 错误请求错误：

@owner_only
async def cmd_bootybomb(self, user_mentions, channel):
    userid = (str(user_mentions))
    await self.send_message(discord.Object(id = userid), bootybomb) 

变量 bootybomb 已从另一个文件导入，该文件只是一堆设置为一个变量的链接。

我收到的错误是：

Traceback (most recent call last):
  File "C:\Users\pc\Desktop\Gamefolders\BootyBot\BootyBot\musicbot\bot.py", line 1289, in on_message
    response = await handler(**handler_kwargs)
  File "C:\Users\pc\Desktop\Gamefolders\BootyBot\BootyBot\musicbot\bot.py", line 115, in wrapper
    return await func(self, *args, **kwargs)
  File "C:\Users\pc\Desktop\Gamefolders\BootyBot\BootyBot\musicbot\bot.py", line 877, in cmd_bootybomb
    await self.send_message(discord.Object(id = userid), bootybomb)
  File "C:\Users\pc\AppData\Local\Programs\Python\Python35\lib\site-packages\discord\client.py", line 831, in send_message
    data = yield from self.http.send_message(channel_id, content, guild_id=guild_id, tts=tts)
  File "C:\Users\pc\AppData\Local\Programs\Python\Python35\lib\site-packages\discord\http.py", line 137, in request
    raise HTTPException(r, data)
discord.errors.HTTPException: BAD REQUEST (status code: 400)

为什么会发生这种情况以及如何解决？