Comment 3 for bug 1381295

when we try to call nova.compute.utils.get_image_metadata with context.get_admin_context(), it would raise excetption.
refer to https://review.openstack.org/#/c/101005/

nova/compute/utils.py:
def get_image_metadata(context, image_api, image_id_or_uri, instance):
    image_system_meta = {}
    # In case of boot from volume, image_id_or_uri may be None
    if image_id_or_uri is not None:
        # If the base image is still available, get its metadata
        try:
            image = image_api.get(context, image_id_or_uri)
        except (exception.ImageNotAuthorized, >>>>>>>>>>cannot get all exception
                exception.ImageNotFound,
                exception.Invalid) as e:
            LOG.warning(_LW("Can't access image %(image_id)s: %(error)s"),
                        {"image_id": image_id_or_uri, "error": e},
                        instance=instance)
        else:
            flavor = flavors.extract_flavor(instance)
            image_system_meta = utils.get_system_metadata_from_image(image,
                                                                     flavor)

    # Get the system metadata from the instance
    system_meta = utils.instance_sys_meta(instance)

    # Merge the metadata from the instance with the image's, if any
    system_meta.update(image_system_meta)

    # Convert the system metadata to image metadata
    return utils.get_image_from_system_metadata(system_meta)