This container can be pulled via:
  docker pull registry.opensuse.org/devel/kubic/containers/container/kubic/etcd:3.5.15-0.6.157
  docker pull registry.opensuse.org/devel/kubic/containers/container/kubic/etcd:3.5.15-1.6.157

Set DOCKER_CONTENT_TRUST=1 to enable image tag verification.