PEP8 cleanups, remove unused imports

apps/common/__init__.py

@@ -5,7 +5,6 @@ import tempfile
 from django.utils.translation import ugettext_lazy as _
 from django.contrib.auth import models as auth_models
 from django.contrib.auth.management import create_superuser
-from django.db.models import signals
 from django.dispatch import receiver
 from django.db.models.signals import post_syncdb