fix missing imports

categories/views.py

@@ -1,9 +1,12 @@
 import django
 from django.shortcuts import get_object_or_404
+from django.core.exceptions import ObjectDoesNotExist
 from django.template import RequestContext
 from django.http import HttpResponse, Http404
 from django.views.decorators.cache import cache_page
 from django.template.loader import select_template
+from django.utils.translation import ugettext as _
+
 from categories.models import Category
 from settings import CACHE_VIEW_LENGTH