* Instead of checking on the filename, we look for a specially named
exported symbol somewhere in a module that's already loaded.
* This allows us to mark the python module as a replay program, so if
it's loaded into the python interpreter it will be able to use the
replay API.
* In future we could handle async exceptions by storing the exception
information in a std::function derived object (instead of the separate
ExceptionHandling that lives on the stack) and query it out in a new
WaitForInvoke function maybe. Right now we just print the exception
to the output log and abort the callback.
baldurk