add X react to our messages as a cue for users who don't know how to delete it

bot.py

@@ -51,7 +51,11 @@ async def on_message(message):
                 print('error reading attachments: {0}'.format(e), file=sys.stderr)
                 return
             try:
-                await message.channel.send("{0} says: {1}".format(message.author.mention, message.content), files=attachments)
+                spoilered_message = await message.channel.send("{0} says: {1}".format(message.author.mention, message.content), files=attachments)
+                try:
+                    await spoilered_message.add_reaction('❌')
+                except discord.DiscordException as e:
+                    print('error reacting to message: {0}'.format(e))
             except discord.DiscordException as e:
                 print('error sending message: {0}'.format(e), file=sys.stderr)
                 return