[1.2.X] Fixed #10728 -- corrected subclassing of Fields who use the SubfieldBase metaclass. Thanks to G2P and George Sakkis for their work on the patch. Backport of [14443].

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@14444 bcc190cf-cafb-0310-a4f2-bffc1f526a37

tests/modeltests/field_subclassing/fields.py

@@ -50,6 +50,9 @@ class SmallField(models.Field):
             return []
         raise TypeError('Invalid lookup type: %r' % lookup_type)
 
+class SmallerField(SmallField):
+    pass
+
 
 class JSONField(models.TextField):
     __metaclass__ = models.SubfieldBase