This works up until Django 1.6. A new branch exists for 1.6.

sigurdga · sigurdga · commit 8d97d7fb8e63 · 2013-12-08T02:35:07.000+01:00
diff --git a/requirements.txt b/requirements.txt
@@ -1,2 +1,2 @@
-django
+django<1.6
 pillow
