[packman] Error when importing Packman repomd.xml.key

[S.]

Hi there, I'm struggling with a really weird error on a spin that I generate based on openSUSE Leap 15.3 + Packman, built with Kiwi. Both during the Kiwi image customization script and in the generated system, it is unable to import the Packman repomd.xml.key (https://ftp.gwdg.de/pub/linux/misc/packman/suse/openSUSE_Leap_15.3/repodata/repomd.xml.key) It just gives me a nondescript error:

> :~> rpm --import /etc/zypp/repos.d/repomd.xml.key
>> error: /etc/zypp/repos.d/repomd.xml.key: key 1 import failed.

There are several keys for other 3rd party and official openSUSE repos that are also imported in the exact same way, and they work fine. Also, if I add the Packman repo via YaST Repositories and accept the automatic prompt to import the key it also works fine.

This exact same Kiwi recipe with the same keys worked fine back in June when I release my last set of ISOs. So all I can figure is there was an update to GPG or RPM or something that has broken this. But I'm stumped. Any ideas?

Thanks a lot!