docs: def read_xdg_config_dirs(name, extension):
      """
      Read from files found in XDG-specified system-wide configuration paths,
      defaulting to ``/etc/xdg``. Depends on ``XDG_CONFIG_DIRS`` environment
      variable.
  
      :param name: application or configuration set name
      :param extension: file extension to look for
      :return: a `.Configuration` instance with values read from XDG-specified
          directories
      """
      # find optional value of ${XDG_CONFIG_DIRS}
      config_dirs = environ.get('XDG_CONFIG_DIRS')
      if config_dirs:
          # PATH-like env vars operate in decreasing precedence, reverse this path set to mimic the end result
          config_dirs = reversed(config_dirs.split(path.pathsep))
      else:
          # XDG spec: "If $XDG_CONFIG_DIRS is either not set or empty, a value equal to /etc/xdg should be used."
          config_dirs = ['/etc/xdg']
  
      # load a file from all config dirs, default to NotConfigured
      fname = '{name}.{extension}'.format(name=name, extension=extension)
      return loadf(*(path.join(config_dir, fname) for config_dir in config_dirs),
                   default=NotConfigured)