This container can be pulled via:
  docker pull registry.opensuse.org/devel/kubic/containers/container/kubic/etcd:3.3
  docker pull registry.opensuse.org/devel/kubic/containers/container/kubic/etcd:3.3.11
  docker pull registry.opensuse.org/devel/kubic/containers/container/kubic/etcd:3.3.11-6.55

Set DOCKER_CONTENT_TRUST=1 to enable image tag verification.