$ osc build --root=/data/build/kbuild-x86_64 Fedora_25 x86_64
openorienteering-mapper.spec 
Building openorienteering-mapper.spec for Fedora_25/x86_64
Getting buildinfo from server and store to
/dev/shm/home:LPechacek:branches:home:dg0yt:staging/openorienteering-mapper/.osc/_buildinfo-Fedora_25-x86_64.xml
Getting buildconfig from server and store to
/dev/shm/home:LPechacek:branches:home:dg0yt:staging/openorienteering-mapper/.osc/_buildconfig-Fedora_25-x86_64
Updating cache of required packages
0.0% cache miss. 397/397 dependencies cached.

Verifying integrity of cached packages
using keys from Fedora:25
warning:
/var/tmp/osbuild-packagecache/Fedora:25/standard/x86_64/acl-2.2.52-11.fc24.x86_64.rpm:
Header V3 RSA/SHA256 Signature, key ID fdb19c98: NOKEY
/var/tmp/osbuild-packagecache/Fedora:25/standard/x86_64/acl-2.2.52-11.fc24.x86_64.rpm
: public key not available
/var/tmp/osbuild-packagecache/Fedora:25/standard/x86_64/attr-2.4.47-16.fc24.x86_64.rpm
: public key not available
/var/tmp/osbuild-packagecache/Fedora:25/standard/x86_64/bash-4.3.43-4.fc25.x86_64.rpm
: public key not available
/var/tmp/osbuild-packagecache/Fedora:25/standard/x86_64/bzip2-1.0.6-20.fc24.x86_64.rpm
: public key not available
....
$ gpg --import --dry-run "/var/tmp/osbuild-packagecache/Fedora:25/_pubkey"
gpg: key 2EC29951: public key "[User ID not found]" imported
gpg: Total number processed: 1
gpg:               imported: 1  (RSA: 1)
gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model
gpg: depth: 0  valid:   4  signed:   8  trust: 0-, 0q, 0n, 0m, 0f, 4u
gpg: depth: 1  valid:   8  signed:   4  trust: 5-, 0q, 0n, 0m, 3f, 0u
gpg: depth: 2  valid:   2  signed:   2  trust: 2-, 0q, 0n, 0m, 0f, 0u
gpg: next trustdb check due at 2020-10-07