Comment # 3 on bug 1207683 from Dominik Heidler

My idea from the opi bugzilla ticket:

On "zypper rr $repo" zypper could:
1. Get the gpgkey entry from the repo file
2. Query it (or better have it's content cached)
3. Compare the queried gpg key with the gpg keys in the rpm db to find the
right one
4. Check if that key is still in use by other repos
5. Remove the key