Index: django/db/models/manager.py
===================================================================
--- django/db/models/manager.py (revision 4647)
+++ django/db/models/manager.py (working copy)
@@ -11,6 +11,10 @@
     # Import copy of _thread_local.py from Python 2.4
     from django.utils._threading_local import local

+# For Python 2.3
+if not hasattr(__builtins__, 'set'):
+    from sets import Set as set
+
 # Size of each "chunk" for get_iterator calls.
 # Larger values are slightly faster at the expense of more storage space.
 GET_ITERATOR_CHUNK_SIZE = 100