With the next two patches, it's possible to log in with demo.py running
under Python 3, both as demo/demo (patch 68) and as admin/admin (patch 69).

68. Python 3 preparation: use bytes in _gen_sid.

69. Python 3 preparation: avoid assigning to instance __getitem__ in
TruthDict.

In Python 3, special method names are generally only looked up at the
class level, not on instance objects, and so assigning to them for an
instance object doesn't work as expected.