I updated the libbash pull request for both function to follow the logic we discussed
we will output missing/invlid parts to stdout and output error code upon completion
so a script will use it in this manner

# Check that all required commmands are installed
if ! missingCMDs=$(EnsureCommandsAvailable "s3cmd mysql mysqldump innobackupex hostname mkdir rm mv sed")
then
    echo "The following system commands could not be found:";
    echo "    $(echo ${missingCMDs[@]} | sed 's/^/--/g ; s/\ /\ --/g')";
    echo "";
    exit 1;
fi