Ticket #12643: 12833.diff

docs/ref/forms/validation.txt

@@ -91 +91 @@
       ``non_field_errors()`` method if you need to. If you want to attach
       errors to a specific field in the form, you will need to access the
       ``_errors`` attribute on the form, which is `described later`_.
+      
+      Also note that there are special considerations when overriding the
+      ``clean()`` method of a ``ModelForm`` subclass. (see the :ref:`ModelForm
+      documentation <topics-forms-modelforms>` 
+      for more information)
 
 These methods are run in the order given above, one field at a time.  That is,
 for each field in the form (in the order they are declared in the form