Bruce noted that the use of err(), fixed to errx() in the last commit, did not specify an exit code.  This implies the use of either a hand- rolled err() (Bruce's suggestion) or a random error code (my suggestion), both of which are against the style guidelines.  This commit specifies the correct error code (implicitly).  This also changes the error message to be a little more helpful.
Bruce noted that the use of err(), fixed to errx() in the last commit,
did not specify an exit code.  This implies the use of either a hand-
rolled err() (Bruce's suggestion) or a random error code (my suggestion),
both of which are against the style guidelines.  This commit specifies
the correct error code (implicitly).  This also changes the error message
to be a little more helpful.

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase