1030604: print to stdout instead of stderr for consistency

An exit code of 1 should not go to stderr as it is a less
severe error. An attempt to modify a blacklisted override
is not a severe exception, so print the message to stdout
and exit with code 1.
Merge pull request #844 from candlepin/mstead/1030604-print-to-stdout

1030604: print to stdout instead of stderr for consistency