This container can be pulled via:
  docker pull registry.opensuse.org/devel/bci/tumbleweed/containerfile/opensuse/alertmanager:0.31
  docker pull registry.opensuse.org/devel/bci/tumbleweed/containerfile/opensuse/alertmanager:0.31.1
  docker pull registry.opensuse.org/devel/bci/tumbleweed/containerfile/opensuse/alertmanager:0.31.1-404.13
  docker pull registry.opensuse.org/devel/bci/tumbleweed/containerfile/opensuse/alertmanager:latest

Set DOCKER_CONTENT_TRUST=1 to enable image tag verification.