Bug#745735: apt: Provide meaningful exit codes for gpg failures

[Micah Anderson <micah@debian.org>]

Package: apt
Version: 1.0.1
Severity: normal

Hello,

It seems like from reading the code that the gpg signature verification process doesn't
provide meaningful exit codes when bad things happen. This results in apt-get update
providing an exit code of zero, even if there was a BADSIG. It would be very useful
if we could get an exit code when these bad situations happen:

BADSIG
NO_PUBKEY
KEYEXPIRED
REVKEYSIG
NODATA

Thank you,
micah

-- System Information:
Debian Release: jessie/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 3.13-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.utf8, LC_CTYPE=en_US.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages apt depends on:
ii  debian-archive-keyring  2012.4
ii  gnupg                   1.4.16-1.1
ii  libapt-pkg4.12          1.0.1
ii  libc6                   2.18-4
ii  libgcc1                 1:4.9-20140411-2
ii  libstdc++6              4.9-20140411-2

apt recommends no packages.

Versions of packages apt suggests:
pn  apt-doc     <none>
ii  aptitude    0.6.10-1
ii  dpkg-dev    1.17.7
ii  python-apt  0.9.3.5

-- no debconf information