apt-get wrong exit status on GPG error

apt-get update return zero exit status on GPG error, as result APT::Update::Post-Invoke-Success create wrong timestamp

to reproduce just add some repository without GPG key and run:
apt-get update; echo $?

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: apt 0.8.16~exp12ubuntu10.12
ProcVersionSignature: Ubuntu 3.2.0-51.77-generic-pae 3.2.48
Uname: Linux 3.2.0-51-generic-pae i686
ApportVersion: 2.0.1-0ubuntu17.4
Architecture: i386
Date: Thu Sep 5 10:17:36 2013
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=uk_UA.UTF-8
 SHELL=/bin/bash
SourcePackage: apt
UpgradeStatus: No upgrade log present (probably fresh install)