message: create the directory if missing
diff: @@ -84,6 +84,11 @@ impl Lock {
  }
  fn acquire(&self) -> Result<()> {
  + if let Some(dir) = self.lock_path().parent() {
  + if ! dir.is_dir() {
  + fs::create_dir_all(dir)?;
  + }
  + }
  let mut file = OpenOptions::new()
  .write(true)
  .create_new(true)
  