'Determine what image should be used to boot the rescue VM.'

def _get_rescue_image(self, context, instance, rescue_image_ref=None):

    if (not rescue_image_ref):
        system_meta = utils.instance_sys_meta(instance)
        rescue_image_ref = system_meta.get('image_base_image_ref')
    if (not rescue_image_ref):
        LOG.warning("Unable    to    find    a    different    image    to    use    for    rescue    VM,    using    instance's    current    image", instance=instance)
        rescue_image_ref = instance.image_ref
    return objects.ImageMeta.from_image_ref(context, self.image_api, rescue_image_ref)
