This container can be pulled via:
  docker pull registry.opensuse.org/isv/rancher/elemental/devgit/containers/rancher/seedimage-builder:1.7.0-dev
  docker pull registry.opensuse.org/isv/rancher/elemental/devgit/containers/rancher/seedimage-builder:1.7.0-dev-4.1
  docker pull registry.opensuse.org/isv/rancher/elemental/devgit/containers/rancher/seedimage-builder:latest

Set DOCKER_CONTENT_TRUST=1 to enable image tag verification.