Fixed #14234 -- Re-validating a model instance added via ModelForm no longer throws spurious PK uniqueness errors. Thanks to David Reynolds and Jeremy Dunck.

Also moved Model._adding to Model._state.adding to reduce instance namespace footprint.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14612 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/forms/models.py

@@ -254,10 +254,10 @@ class BaseModelForm(BaseForm):
             # if we didn't get an instance, instantiate a new one
             self.instance = opts.model()
             object_data = {}
-            self.instance._adding = True
+            self.instance._state.adding = True
         else:
             self.instance = instance
-            self.instance._adding = False
+            self.instance._state.adding = False
             object_data = model_to_dict(instance, opts.fields, opts.exclude)
         # if initial was provided, it should override the values from instance
         if initial is not None: