Fixed #12698. Model.clean() used with a ModelForm no longer causes a KeyError when raising a ValidationError.

Note that previously it was possible to raise a ValidationError in the same place with a message_dict attribute. That behavior was a bug and will no longer have the same behavior.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12402 bcc190cf-cafb-0310-a4f2-bffc1f526a37

tests/regressiontests/model_forms_regress/models.py

@@ -1,5 +1,7 @@
 import os
 from django.db import models
+from django.core.exceptions import ValidationError
+
 
 class Person(models.Model):
     name = models.CharField(max_length=100)
@@ -37,3 +39,11 @@ class CustomFileField(models.FileField):
 
 class CustomFF(models.Model):
     f = CustomFileField(upload_to='unused', blank=True)
+
+class RealPerson(models.Model):
+    name = models.CharField(max_length=100)
+
+    def clean(self):
+        if self.name.lower() == 'anonymous':
+            raise ValidationError("Please specify a real name.")
+