Attempt sending an error message directly to the user, when permissions are missing

[kevinkjt2000]

bowser_1  |   File "/root/.pex/install/discord.py-0.16.12-py3-none-any.whl.a649d6afc6aae103cb71b078e2dbb017b4a5c28e/discord.py-0.16.12-py3-none-any.whl/discord/client.py", line 1152, in send_message
bowser_1  |     data = yield from self.http.send_message(channel_id, content, guild_id=guild_id, tts=tts, embed=embed)
bowser_1  |   File "/root/.pex/install/discord.py-0.16.12-py3-none-any.whl.a649d6afc6aae103cb71b078e2dbb017b4a5c28e/discord.py-0.16.12-py3-none-any.whl/discord/http.py", line 196, in request
bowser_1  |     raise Forbidden(r, data)
bowser_1  | discord.errors.Forbidden: FORBIDDEN (status code: 403): Missing Permissions

The above log messages are never shown to the user; instead the user sees nothing when bowser responds to a command on a channel where bowser lacks the permission for sending messages.

Attempting to send a DM in this case is possibly the best way to let the user know that this permission error is happening. And if sending this warning message fails, there is probably nothing else bowser could do in this case.