raise exception on clean_location failure

smash/web/forms/appointment_form.py

@@ -105,7 +105,7 @@ class AppointmentEditForm(AppointmentForm):
         location = self.cleaned_data['location']
         if self.user.locations.filter(id=location.id).count() == 0:
             self.add_error('location', "You cannot create appointment for this location")
-            return None
+            raise forms.ValidationError("You cannot create appointment for this location")
         else:
             return location