PEP8 Cleanups.

mayan/apps/common/mixins.py

@@ -5,7 +5,6 @@ from django.contrib import messages
 from django.core.exceptions import PermissionDenied
 from django.core.urlresolvers import reverse
 from django.http import HttpResponseRedirect
-from django.shortcuts import get_object_or_404
 from django.utils.translation import ungettext
 
 from acls.models import AccessControlList