Fixed circular reference problem from CC project. Caused by import of

model from within forms.validators

oscar/apps/checkout/views.py

         """
         # Check that shipping address has been completed
         if not self.checkout_session.is_shipping_address_set():
-            messages.error(request, _("Please choose a shipping address"))
+            messages.error(self.request, _("Please choose a shipping address"))
             return HttpResponseRedirect(reverse('checkout:shipping-address'))
         # Check that shipping method has been set
         if not self.checkout_session.is_shipping_method_set():
-            messages.error(request, _("Please choose a shipping method"))
+            messages.error(self.request, _("Please choose a shipping method"))
             return HttpResponseRedirect(reverse('checkout:shipping-method'))
         # Next, check that basket isn't empty
         if basket.is_empty:

oscar/core/validators.py

 
 from django.db.models import get_model
 
-# FlatPages is None if not installed
-FlatPage = get_model('flatpages', 'FlatPage')
-
 
 class ExtendedURLValidator(validators.URLValidator):
     def __call__(self, value):
                 resolve(value)
             self.is_local_url = True
         except Http404:
-            # check for existing urls of flatpages if package installed
+            # FlatPages is None if not installed
+            FlatPage = get_model('flatpages', 'FlatPage')
             if FlatPage is not None:
                 for page in FlatPage.objects.all().only(('url')):
                     if value == page.url: