I'm not pickling/unpickling it directly, I'm using multiprocessing to handle queries to my server in worker processes which is using pickle to propagate exceptions raised in the worker to the parent.

I could instead raise a different exception and wrap it in a Fault later (which is what I ended up doing to avoid the issue), but it seems like a case of "to-may-to" vs. "to-mah-to".  Either way an Exception should be able to be propagated up to the parent in multiprocessing, whether it's my own or Fault.