Return failure code on failure; DM-1027

This bit doesn't bother me (setting PRINT_CMD_LINE_FUNC does --- if it were a unix command I could just prefix it with @ like in make).

I create an Action (checkTestStatus_command) and ask that it always run, but only when everything else has finished.  I could register an atexit handler to do this (at the python level) but by then it's too late to just call sys.exit(1) --- the multiprocess cleanup complains.