docs: def _build_machine_uri(machine, cwd):
      '''
      returns string used to fetch id names from the sdb store.
  
      the cwd and machine name are concatenated with '?' which should
      never collide with a Salt node id -- which is important since we
      will be storing both in the same table.
      '''
      key = '{}?{}'.format(machine, os.path.abspath(cwd))
      return _build_sdb_uri(key)