Fixed #21132 -- Removed the useless app_name argument to AdminSite.

Thanks MarkusH for the report and Florian for review.

django/contrib/admin/sites.py

@@ -49,10 +49,9 @@ class AdminSite(object):
     password_change_template = None
     password_change_done_template = None
 
-    def __init__(self, name='admin', app_name='admin'):
+    def __init__(self, name='admin'):
         self._registry = {}  # model_class class -> admin_class instance
         self.name = name
-        self.app_name = app_name
         self._actions = {'delete_selected': actions.delete_selected}
         self._global_actions = self._actions.copy()
 
@@ -263,7 +262,7 @@ class AdminSite(object):
 
     @property
     def urls(self):
-        return self.get_urls(), self.app_name, self.name
+        return self.get_urls(), 'admin', self.name
 
     def each_context(self):
         """

docs/releases/1.8.txt

@@ -492,6 +492,11 @@ Miscellaneous
   ``'username'``, using the the ``'unique'`` key in its
   :attr:`~django.forms.Field.error_messages` argument.
 
+* ``AdminSite`` no longer takes an ``app_name`` argument and its ``app_name``
+  attribute has been removed. The application name is always ``admin`` (as
+  opposed to the instance name which you can still customize using
+  ``AdminSite(name="...")``.
+
 .. _deprecated-features-1.8:
 
 Features deprecated in 1.8