Reorder the __all__ variable. Fix reporting return codes from the subprocess (generating an exception does not work)

This will spawn a thread to monitor the subprocess, capture both

stdout and stderr and throw an exception if the process terminates

with a non-zero error code.

Manual testing was done by having it call a script that slept for 30s and verifying that other requests could be successfully made to rolekit while it was waiting.
This code probably needs a unit test, but I haven't written it yet.