Subject: irrelevant...

From: KatolaZ <[email-masked]>
Date: Fri, 14 Apr 2017 10:57:00 +0100

I am gonna close his one. You fail to verify source package signatures
since you don't have the corresponding developer (or distro) key in
your keyring. If you import the key in your trustedkeys.gpg, it
doesn't fail any more.