docs: def required_from_env(key):
      """
      Retrieve a required variable from the current environment variables.
  
      Raises a ValueError if the env variable is not found or has no value.
  
      """
      val = os.environ.get(key)
      if not val:
          raise ValueError(
              "Required argument '{}' not supplied and not found in environment variables".format(key))
      return val