This container can be pulled via:
  docker pull registry.opensuse.org/isv/rancher/elemental/dev/containers_next/rancher/seedimage-builder:1.4.0
  docker pull registry.opensuse.org/isv/rancher/elemental/dev/containers_next/rancher/seedimage-builder:1.4.0-48.2
  docker pull registry.opensuse.org/isv/rancher/elemental/dev/containers_next/rancher/seedimage-builder:latest

Set DOCKER_CONTENT_TRUST=1 to enable image tag verification.