How to update the systemtap keyring:

update systemtap version in specfile to new version
run 'osc service localrun download_files' to download the new tarball and signatrure files
run 'gpg systemtap-${ver}.tar.gz.sig' -- look for "gpg: Signature made {date} using RSA key ID {key}" in output
run 'gpg --recv-key $key' to obtain the key from the public keyserver
run 'gpg --export --armor --output systemtap.keyring $key'

How to verify against the keyring:
run 'gpg --keyring systemtap.keyring systemtap-${ver}.tar.gz.sig'