Unfortunately debian/sid does not build on sid, the tests fail: "IndexError: index 5 is out of bounds for axis 0 with size 2" - I don't think this is anything I did. It builds fine on Jessie.
Seems Django 1.7.x is incompatible with numpy 1.9 in Debian/sid.
This is the fix by upstream, will file a properly bug report against Django and fix.