Description of problem:

The official operator catalog images that are referenced in the documentation [1] are not build / published with signatures. This breaks the "opm index prune" command if the policy.json is configured according to article https://access.redhat.com/articles/3116561.

[1] https://docs.openshift.com/container-platform/4.6/operators/admin/olm-restricted-networks.html#olm-understanding-operator-catalog-images_olm-restricted-networks

Version-Release number of selected component (if applicable):

[stack@osp16amd ocp-test4]$ opm version
Version: version.Version{OpmVersion:"v1.15.3", GitCommit:"9e92474", BuildDate:"2020-12-03T18:34:29Z", GoOs:"linux", GoArch:"amd64"}
[stack@osp16amd ocp-test4]$ oc version --client
Client Version: 4.7.0-rc.2

opm index prune:

~~~
[stack@osp16amd ocp-test4]$ opm index prune -f registry.redhat.io/redhat/redhat-operator-index:v4.6 -p elasticsearch-operator,cluster-logging -t 192.168.100.98:443/olm/redhat-operator-index-logging:v4.6 
INFO[0000] pruning the index                             packages="[elasticsearch-operator cluster-logging]"
INFO[0000] Pulling previous image registry.redhat.io/redhat/redhat-operator-index:v4.6 to get metadata  packages="[elasticsearch-operator cluster-logging]"
INFO[0000] running /usr/bin/podman pull registry.redhat.io/redhat/redhat-operator-index:v4.6  packages="[elasticsearch-operator cluster-logging]"
ERRO[0003] Trying to pull registry.redhat.io/redhat/redhat-operator-index:v4.6...
  A signature was required, but no signature exists
Error: error pulling image "registry.redhat.io/redhat/redhat-operator-index:v4.6": unable to pull registry.redhat.io/redhat/redhat-operator-index:v4.6: unable to pull image: Source image rejected: A signature was required, but no signature exists  packages="[elasticsearch-operator cluster-logging]"
Error: error pulling image: Trying to pull registry.redhat.io/redhat/redhat-operator-index:v4.6...
  A signature was required, but no signature exists
Error: error pulling image "registry.redhat.io/redhat/redhat-operator-index:v4.6": unable to pull registry.redhat.io/redhat/redhat-operator-index:v4.6: unable to pull image: Source image rejected: A signature was required, but no signature exists
. exit status 125
~~~

How reproducible:

Always

Steps to Reproduce:
1. Configure policy according to https://access.redhat.com/articles/3116561
2. Try to pull images

~~~
[stack@osp16amd ocp-test4]$ cat /etc/containers/registries.d/registry.redhat.io.yaml 
docker:
     registry.redhat.io:
         sigstore: https://registry.redhat.io/containers/sigstore
[stack@osp16amd ocp-test4]$ cat /etc/containers/policy.json 
{
  "default": [
    {
      "type": "insecureAcceptAnything"
    }
  ],
  "transports": {
    "docker": {
      "registry.redhat.io": [
        {
          "type": "signedBy",
          "keyType": "GPGKeys",
          "keyPath": "/etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release"
        }
      ]
    },
    "docker-daemon": {
      "": [
        {
          "type": "insecureAcceptAnything"
        }
      ]
    }
  }
}
~~~

Pull fails with "unable to pull image: Source image rejected: A signature was required, but no signature exists"
~~~
[stack@osp16amd ocp-test4]$ for i in registry.redhat.io/redhat/redhat-operator-index:v4.6 registry.redhat.io/redhat/certified-operator-index:v4.6 registry.redhat.io/redhat/redhat-marketplace-index:v4.6 registry.redhat.io/redhat/community-operator-index:latest; do podman pull --authfile pull-secret.json $i; done
Trying to pull registry.redhat.io/redhat/redhat-operator-index:v4.6...
  A signature was required, but no signature exists
Error: error pulling image "registry.redhat.io/redhat/redhat-operator-index:v4.6": unable to pull registry.redhat.io/redhat/redhat-operator-index:v4.6: unable to pull image: Source image rejected: A signature was required, but no signature exists
Trying to pull registry.redhat.io/redhat/certified-operator-index:v4.6...
  A signature was required, but no signature exists
Error: error pulling image "registry.redhat.io/redhat/certified-operator-index:v4.6": unable to pull registry.redhat.io/redhat/certified-operator-index:v4.6: unable to pull image: Source image rejected: A signature was required, but no signature exists
Trying to pull registry.redhat.io/redhat/redhat-marketplace-index:v4.6...
  A signature was required, but no signature exists
Error: error pulling image "registry.redhat.io/redhat/redhat-marketplace-index:v4.6": unable to pull registry.redhat.io/redhat/redhat-marketplace-index:v4.6: unable to pull image: Source image rejected: A signature was required, but no signature exists
Trying to pull registry.redhat.io/redhat/community-operator-index:latest...
  A signature was required, but no signature exists
Error: error pulling image "registry.redhat.io/redhat/community-operator-index:latest": unable to pull registry.redhat.io/redhat/community-operator-index:latest: unable to pull image: Source image rejected: A signature was required, but no signature exists
~~~

Actual results:

Image can not be pulled due to signature missing

Expected results:

Images should be published with signature

Additional info: