Clean django code

django_project/geosight/data/models/context_layer.py

@@ -19,7 +19,6 @@
 
 import requests
 from django.contrib.gis.db import models
-from django.core.exceptions import ValidationError
 from django.db.models.signals import post_save
 from django.dispatch import receiver
 from django.utils.translation import ugettext_lazy as _