Fixed #13206 -- call super().__init__() in Model.__init__ to allow mixins to do things there.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15317 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/base.py

@@ -1,6 +1,7 @@
 import types
 import sys
 from itertools import izip
+
 import django.db.models.manager     # Imported to register signal handler.
 from django.core.exceptions import ObjectDoesNotExist, MultipleObjectsReturned, FieldError, ValidationError, NON_FIELD_ERRORS
 from django.core import validators
@@ -361,6 +362,7 @@ class Model(object):
                     pass
             if kwargs:
                 raise TypeError("'%s' is an invalid keyword argument for this function" % kwargs.keys()[0])
+        super(Model, self).__init__()
         signals.post_init.send(sender=self.__class__, instance=self)
 
     def __repr__(self):