Ticket #8245: Misleading-AlreadyRegistered-03.diff

django/contrib/admin/__init__.py

@@ -9 +9 @@
     may want.
     """
     import imp
+    import copy
     from django.conf import settings
     for app in settings.INSTALLED_APPS:
         try:
@@ -16 +17 @@
         except ImportError:
             # there is no app admin.py, skip it
             continue
-        __import__("%s.admin" % app)
+        try:
+            model_registry_before_import = copy.copy(site._registry)
+            __import__("%s.admin" % app)
+        except:
+            # Reset the model registry to the state before the last import as this import will have to reoccur
+            # on the next request and this could raise NotRegistered and AlreadyRegistered exceptions (see #8245).
+            site._registry = model_registry_before_import
+            raise