def get_builder_image_id(self):

        try:
            buildroot_tag = os.environ["OPENSHIFT_CUSTOM_BUILD_BASE_IMAGE"]
        except KeyError:
            return ''

        try:
            pod = self.osbs.get_pod_for_build(self.build_id)
            all_images = pod.get_container_image_ids()
        except OsbsException as ex:
            self.log.error("unable to find image id: %r", ex)
            return buildroot_tag

        try:
            return all_images[buildroot_tag]
        except KeyError:
            self.log.error("Unable to determine buildroot image ID for %s",
                           buildroot_tag)
            return buildroot_tag
Find out the docker ID of the buildroot image we are in.
dataset/ETHPy150Open projectatomic/atomic-reactor/atomic_reactor/plugins/exit_koji_promote.py/KojiPromotePlugin.get_builder_image_id