Comment # 3 on bug 902823 from Michael Andres

That's pretty strange, a non-zypp::Exception thrown within the signature
verification workflow. The next step after 

> giskard(19104) [zypp::KeyRing] KeyRing.cc(getData):154 Found keys: {
> giskard(19104) [zypp::KeyRing] KeyRing.cc(getData):154   [2E85BAEE9EBD09C4-5040cc8f] [KDE:Unstable OBS Project <KDE:Unstable@build.opensuse.org>] [4A3E075626347342E1A3F2572E85BAEE9EBD09C4] [T
TL 12]
> giskard(19104) [zypp::KeyRing] KeyRing.cc(getData):154 }

would have been to execute "'/usr/bin/gpg2' '--verify' ...", but some exception
happened before. It's not reproduceable  for me, nor is there some hint in the
log snippet. 

@Luca: 
Could you please attache the complete log of the above command. If you have
zypper-log installed, simply run 'zypper-log 19104' (or 'zypper-log -r 1 19104'
if the og already rotated).