code: func (fo *FileWriterOutput) fallbackLog(tmpl string, args ...interface{}) {
  	fmt.Fprintf(os.Stderr, tmpl, args...)
  }
docs: // Try to communicate a message without using our log file. In all likelihood,
  // stderr is closed or redirected to /dev/null, but at least we can try
  // writing there. In the very worst case, if an admin attaches a ptrace to
  // this process, it will be more clear what the problem is.