do not display confirmation page if already validated

newsletter/views.py

@@ -44,7 +44,7 @@ class ConfirmationView(TemplateView):
 
     def get_context_data(self, token, **kwargs):
         context = super(ConfirmationView, self).get_context_data(**kwargs)
-        subscriber = get_object_or_404(Subscriber, password=token, is_registered=None)
+        subscriber = get_object_or_404(Subscriber, password=token, is_validated=False)
         subscriber.is_validated = True
         subscriber.save()
         subscriber.subscribe_in_mailman()