From 1e9251cfefe5e4ce70094b90c000334ca431e954 Mon Sep 17 00:00:00 2001
From: Rapptz <rapptz@gmail.com>
Date: Wed, 10 Aug 2016 15:09:07 -0400
Subject: [PATCH] [commands] Delete module when it does not have a setup
 function.

---
 discord/ext/commands/bot.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/discord/ext/commands/bot.py b/discord/ext/commands/bot.py
index 7250f3a68..d9e02f1fe 100644
--- a/discord/ext/commands/bot.py
+++ b/discord/ext/commands/bot.py
@@ -712,6 +712,8 @@ class Bot(GroupMixin, discord.Client):
 
         lib = importlib.import_module(name)
         if not hasattr(lib, 'setup'):
+            del lib
+            del sys.modules[name]
             raise discord.ClientException('extension does not have a setup function')
 
         lib.setup(self)