Currently, I'm monkey patching _safe_key (adding a try/except) as follows:

>>> import pprint
>>>
>>> class _safe_key(pprint._safe_key):
>>>     def __lt__(self, other):
>>>         try:
>>>             rv = self.obj.__lt__(other.obj)
>>>         except TypeError:   # Exception instead of TypeError?
>>>             rv = NotImplemented
>>> 
>>>         if rv is NotImplemented:
>>>             rv = (str(type(self.obj)), id(self.obj)) < \
>>>                  (str(type(other.obj)), id(other.obj))
>>>         return rv
>>>         
>>> pprint._safe_key = _safe_key
>>> 
>>> pprint.pprint({(0,): 1, (None,): 2})
{(None,): 2, (0,): 1}