code: func NewUsageExitError(message string, ctx *cli.Context) error {
  	if wordRegex.MatchString(message[len(message)-1:]) {
  		message += "."
  	}
  	return cli.NewExitError(message+"\n"+usageString(ctx), -1)
  }
docs: // NewUsageExitError creates an ExitError with appended usage text