[commands] Fix Context.command_failed from being incorrect.

When used, it would be set to False after the invoke was done. Ideally
it should report to False during invoke but True during any error
case.

discord/ext/commands/bot.py

@@ -742,7 +742,6 @@ class BotBase(GroupMixin):
             except CommandError as e:
                 yield from ctx.command.dispatch_error(ctx, e)
             else:
-                ctx.command_failed = False
                 self.dispatch('command_completion', ctx)
         elif ctx.invoked_with:
             exc = CommandNotFound('Command "{}" is not found'.format(ctx.invoked_with))

discord/ext/commands/context.py

@@ -83,7 +83,7 @@ class Context(discord.abc.Messageable):
         self.invoked_with = attrs.pop('invoked_with', None)
         self.invoked_subcommand = attrs.pop('invoked_subcommand', None)
         self.subcommand_passed = attrs.pop('subcommand_passed', None)
-        self.command_failed = attrs.pop('command_failed', True)
+        self.command_failed = attrs.pop('command_failed', False)
         self._state = self.message._state
 
     @asyncio.coroutine

discord/ext/commands/core.py

@@ -61,10 +61,13 @@ def hooked_wrapped_callback(command, ctx, coro):
         try:
             ret = yield from coro(*args, **kwargs)
         except CommandError:
+            ctx.command_failed = True
             raise
         except asyncio.CancelledError:
+            ctx.command_failed = True
             return
         except Exception as e:
+            ctx.command_failed = True
             raise CommandInvokeError(e) from e
         finally:
             yield from command.call_after_hooks(ctx)
@@ -165,6 +168,7 @@ class Command:
 
     @asyncio.coroutine
     def dispatch_error(self, ctx, error):
+        ctx.command_failed = True
         cog = self.instance
         try:
             coro = self.on_error