transient network failures during apt-add-repository are fatal

[Francis Ginther]

Saw this on an automated landscape autopilot run:

[from keystone-2:/var/log/juju/unit-landscape-client-52.log]
2017-01-06 15:31:47 INFO juju-log Installing ['apt-transport-https', 'wget'] with options: ['--option=Dpkg::Options:
:=--force-confold']
2017-01-06 15:31:47 INFO install Reading package lists...
2017-01-06 15:31:47 INFO install Building dependency tree...
2017-01-06 15:31:47 INFO install Reading state information...
2017-01-06 15:31:47 INFO install apt-transport-https is already the newest version (1.2.15ubuntu0.2).
2017-01-06 15:31:47 INFO install wget is already the newest version (1.17.1-1ubuntu1.1).
2017-01-06 15:31:47 INFO install 0 upgraded, 0 newly installed, 0 to remove and 9 not upgraded.
2017-01-06 15:31:48 INFO install Cannot add PPA: 'ppa:~landscape/ubuntu/trunk'.
2017-01-06 15:31:48 INFO install ERROR: '~landscape' user or team does not exist.
2017-01-06 15:31:49 INFO install Traceback (most recent call last):
2017-01-06 15:31:49 INFO install File "/var/lib/juju/agents/unit-landscape-client-52/charm/hooks/install", line 92, in <module>
2017-01-06 15:31:49 INFO install sys.exit(hooks.execute(sys.argv))
2017-01-06 15:31:49 INFO install File "/var/lib/juju/agents/unit-landscape-client-52/charm/hooks/charmhelpers/core/hookenv.py", line 598, in execute
2017-01-06 15:31:49 INFO install self._hooks[hook_name]()
2017-01-06 15:31:49 INFO install File "/var/lib/juju/agents/unit-landscape-client-52/charm/hooks/install", line 34, in install
2017-01-06 15:31:49 INFO install add_apt_source(origin)
2017-01-06 15:31:49 INFO install File "/var/lib/juju/agents/unit-landscape-client-52/charm/hooks/install", line 88, in add_apt_source
2017-01-06 15:31:49 INFO install return add_source(url, key)
2017-01-06 15:31:49 INFO install File "/var/lib/juju/agents/unit-landscape-client-52/charm/hooks/charmhelpers/fetch/__init__.py", line 265, in add_source
2017-01-06 15:31:49 INFO install subprocess.check_call(['add-apt-repository', '--yes', source])
2017-01-06 15:31:49 INFO install File "/usr/lib/python3.5/subprocess.py", line 581, in check_call
2017-01-06 15:31:49 INFO install raise CalledProcessError(retcode, cmd)
2017-01-06 15:31:49 INFO install subprocess.CalledProcessError: Command '['add-apt-repository', '--yes', 'ppa:landscape/trunk']' returned non-zero exit status 1
2017-01-06 15:31:49 ERROR juju.worker.uniter.operation runhook.go:107 hook "install" failed: exit status 1

The 'add-apt-repository' error can occur as the result of transient network issues. In this case, it's fatal to the install hook.

[Francis Ginther (fginther)]

Added autopilot-log-analyser to track writing an issue analyser for this error.