Up a queue, by removing a down file -- if a queue has no down file,
       this function is a no-op.

def up(queue, host=None):
    '''Up a queue, by removing a down file -- if a queue has no down file,
       this function is a no-op.'''
    down_path = fsq_path.down(queue, host=host)
    _queue_ok(os.path.dirname(down_path))
    try:
        os.unlink(down_path)
    except (OSError, IOError, ), e:
        if e.errno != errno.ENOENT:
            raise FSQConfigError(e.errno, wrap_io_os_err(e))