If the python version of Persistent had __setstate__ called with a dictionary containing exactly two items, it would fail at idict.update(inst_dict) with 'ValueError: sequence of pairs expected' due to incorrect tuple unpacking. Do what the C version does and check for a tuple explicitly.
Merge branch 'setstate' of https://github.com/NextThought/persistent into NextThought-setstate
Changelog for PR #5.