should retry reading key from keyserver (in _recv_key)

[Scott Moser]

Some recent events have made keyservers less reliable than they were
previously:
      https://bitbucket.org/skskeyserver/sks-keyserver/issues/57
      https://bitbucket.org/skskeyserver/sks-keyserver/issues/60

We have seen a greatly increased failure rate of retreiving keys
from the key servers, both in cloud-init and with using apt-add-repository.

Here is an example failure:
  https://jenkins.ubuntu.com/server/view/cloud-init,%20curtin,%20streams/job/cloud-init-integration-nocloud-kvm-x/191/console

The stdout/stderr that is a result of running:
$ add-apt-repository --yes ppa:cloud-init-devel/daily

gpg: keyring `/tmp/tmp4s88x_yf/secring.gpg' created
gpg: keyring `/tmp/tmp4s88x_yf/pubring.gpg' created
gpg: requesting key E4D304DF from hkp server keyserver.ubuntu.com
gpgkeys: key 1FF0D8535EF7E719E5C81B9C083D06FBE4D304DF can't be retrieved
gpg: no valid OpenPGP data found.
gpg: Total number processed: 0
gpg: keyserver communications error: keyserver helper general error
gpg: keyserver communications error: unknown pubkey algorithm
gpg: keyserver receive failed: unknown pubkey algorithm
Failed to add key.

Retries on reading the key make sense here to be more resilient to
transient network or remote service resources. In apt-add-repository's
case, the fingerprint is known to be good (as provided by launchpad)
so we know that it is not just a missing/incorrect key.

ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: software-properties-common 0.96.24.33
ProcVersionSignature: Ubuntu 4.15.0-23.25-generic 4.15.18
Uname: Linux 4.15.0-23-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.10-0ubuntu3
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Thu Jun 28 22:28:53 2018
EcryptfsInUse: Yes
InstallationDate: Installed on 2015-07-23 (1072 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Alpha amd64 (20150722.1)
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: software-properties
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Valentin Boucher (boucherv29)]

Same issue on Ubuntu 16.04:

sudo add-apt-repository -y ppa:maas/stable

gpg: keyring `/tmp/tmp6wy_3tp8/secring.gpg' created
gpg: keyring `/tmp/tmp6wy_3tp8/pubring.gpg' created
gpg: requesting key 684D4A1C from hkp server keyserver.ubuntu.com
gpgkeys: key 3AB6DCF1F234E78DAA9C104204E7FDC5684D4A1C can't be retrieved
gpg: no valid OpenPGP data found.
gpg: Total number processed: 0
gpg: keyserver communications error: keyserver helper general error
gpg: keyserver communications error: unknown pubkey algorithm
gpg: keyserver receive failed: unknown pubkey algorithm
Failed to add key.

[Scott Moser (smoser)]

I saw this "in the wild" with /var/log/cloud-init.log showing:

2018-07-09 15:20:22,666 - util.py[DEBUG]: Running command ['add-apt-repository', 'cloud-archive:ocata'] with allowed return codes [0] (shell=False, capture=True)
2018-07-09 15:20:24,907 - cc_apt_configure.py[ERROR]: add-apt-repository failed.
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/cloudinit/config/cc_apt_configure.py", line 615, in add_apt_sources
    util.subp(["add-apt-repository", source], target=target)
  File "/usr/lib/python3/dist-packages/cloudinit/util.py", line 1957, in subp
    cmd=args)
cloudinit.util.ProcessExecutionError: Unexpected error while running command.
Command: ['add-apt-repository', 'cloud-archive:ocata']
Exit code: 1
Reason: -
Stdout: Ubuntu Cloud Archive for OpenStack Ocata
         More info: https://wiki.ubuntu.com/ServerTeam/CloudArchive
        Reading package lists...
        Building dependency tree...
        Reading state information...
        Failed to add key.
Stderr: E: Unable to locate package ubuntu-cloud-keyring

[Launchpad Janitor (janitor)]

This bug was fixed in the package software-properties - 0.96.24.35

---------------
software-properties (0.96.24.35) cosmic; urgency=medium

  * Retry on failed lookups of gpg keys (LP: #1779302)

 -- Scott Moser <email address hidden> Tue, 17 Jul 2018 10:55:34 -0400