code: def require_executable(executable: str) -> None:
      
      if shutil.which(executable):
          return
      errmsg = "Missing command (must be on the PATH): " + executable
      log.critical(errmsg)
      raise FileNotFoundError(errmsg)
docs: If ``executable`` is not found by :func:`shutil.which`, raise
      :exc:`FileNotFoundError`.