Fix regression from renaming exception

plugins/qotd.py

             self.host = args.pop(0)
             self.port = args.pop(0) if args else 17
         except IndexError:
-            raise sardine.SardinePluginUsageError("HOST [PORT]")
+            raise sardine.PluginUsageError("HOST [PORT]")
         self.port = int(self.port)
 
     def _fetch_qotd(self):