fail fast if no $CONFIG, and print sanitized $CONFIG
fail fast if no $CONFIG, and print sanitized $CONFIG

[finishes #121014663]
Related: https://github.com/cloudfoundry/cf-release/issues/972

matt-royal/cf-acceptance-tests,matt-royal/cf-acceptance-tests,matt-royal/cf-acceptance-tests,matt-royal/cf-acceptance-tests,matt-royal/cf-acceptance-tests,matt-royal/cf-acceptance-tests,matt-royal/cf-acceptance-tests,matt-royal/cf-acceptance-tests