Having taken this step back, I chose the least universal but most straightforward method and found a way. A
def on_application_quit(): try: popen.kill() except OSError: # Already dead pass cmds.scriptJob( event=["quitApplication", on_application_quit], protected=True )
@derrick, if you
pull you should be able to close Maya with the GUI open. As an added side-effect, the GUI now also closes when the host does.
$ cd pyblish-qml $ git pull