Refs #373 -- Added Model._is_pk_set() abstraction to check if a Model's PK is set.

django/contrib/contenttypes/forms.py

@@ -31,7 +31,7 @@ class BaseGenericInlineFormSet(BaseModelFormSet):
             + self.ct_fk_field.name
         )
         self.save_as_new = save_as_new
-        if self.instance is None or self.instance.pk is None:
+        if self.instance is None or not self.instance._is_pk_set():
             qs = self.model._default_manager.none()
         else:
             if queryset is None:

django/contrib/postgres/constraints.py

@@ -198,7 +198,7 @@ class ExclusionConstraint(BaseConstraint):
             lookups.append(lookup)
         queryset = queryset.filter(*lookups)
         model_class_pk = instance._get_pk_val(model._meta)
-        if not instance._state.adding and model_class_pk is not None:
+        if not instance._state.adding and instance._is_pk_set(model._meta):
             queryset = queryset.exclude(pk=model_class_pk)
         if not self.condition:
             if queryset.exists():