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.

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)