Description of problem:

Since a few days various repos lack repomd.xml.asc

So updating from these repos fails.

E.g.

Error: Failed to download metadata for repo 'appstream': GPG verification is enabled, but GPG signature is not available. This may be an error or the repository does not support GPG verification: Status code: 404 for https://ftp.nsc.ru/pub/centos-9/9-stream/AppStream/x86_64/os/repodata/repomd.xml.asc

being sent over from: https://pagure.io/centos-infra/issue/1243