Fix code style

djangocms_blog/models.py

@@ -8,8 +8,6 @@ from django.conf import settings as dj_settings
 from django.contrib.auth import get_user_model
 from django.core.urlresolvers import reverse
 from django.db import models
-from django.db.models.signals import pre_save
-from django.dispatch import receiver
 from django.utils import timezone
 from django.utils.encoding import force_text, python_2_unicode_compatible
 from django.utils.html import escape, strip_tags