xenial error on config-changed

[James Jesudason]

The config-changed hook is failing in the charmhelper when installing on Xenial:

2016-07-01 17:13:20 INFO config-changed Reading package lists...
2016-07-01 17:13:20 INFO juju-log Installing ['haproxy', 'python-jinja2'] with options: ['--option=Dpkg::Options::=--force-confold']
2016-07-01 17:13:20 INFO config-changed Reading package lists...
2016-07-01 17:13:20 INFO config-changed Building dependency tree...
2016-07-01 17:13:20 INFO config-changed Reading state information...
2016-07-01 17:13:20 INFO config-changed python-jinja2 is already the newest version (2.8-1).
2016-07-01 17:13:20 INFO config-changed haproxy is already the newest version (1.6.3-1ubuntu0.1).
2016-07-01 17:13:20 INFO config-changed 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
2016-07-01 17:13:20 INFO juju-log Installing ['python-pyasn1', 'python-pyasn1-modules'] with options: ['--option=Dpkg::Options::=--force-confold']
2016-07-01 17:13:20 INFO config-changed Reading package lists...
2016-07-01 17:13:20 INFO config-changed Building dependency tree...
2016-07-01 17:13:20 INFO config-changed Reading state information...
2016-07-01 17:13:20 INFO config-changed python-pyasn1 is already the newest version (0.1.9-1).
2016-07-01 17:13:20 INFO config-changed python-pyasn1-modules is already the newest version (0.0.7-0.1).
2016-07-01 17:13:20 INFO config-changed 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
2016-07-01 17:13:20 INFO config-changed Traceback (most recent call last):
2016-07-01 17:13:20 INFO config-changed File "/var/lib/juju/agents/unit-haproxy-5/charm/hooks/config-changed", line 1362, in <module>
2016-07-01 17:13:20 INFO config-changed main(hook_name)
2016-07-01 17:13:20 INFO config-changed File "/var/lib/juju/agents/unit-haproxy-5/charm/hooks/config-changed", line 1320, in main
2016-07-01 17:13:20 INFO config-changed config_changed()
2016-07-01 17:13:20 INFO config-changed File "/var/lib/juju/agents/unit-haproxy-5/charm/hooks/config-changed", line 930, in config_changed
2016-07-01 17:13:20 INFO config-changed haproxy_globals = create_haproxy_globals()
2016-07-01 17:13:20 INFO config-changed File "/var/lib/juju/agents/unit-haproxy-5/charm/hooks/config-changed", line 161, in create_haproxy_globals
2016-07-01 17:13:20 INFO config-changed if has_ssl_support():
2016-07-01 17:13:20 INFO config-changed File "/var/lib/juju/agents/unit-haproxy-5/charm/hooks/config-changed", line 1173, in has_ssl_support
2016-07-01 17:13:20 INFO config-changed cache = apt_cache()
2016-07-01 17:13:20 INFO config-changed File "/var/lib/juju/agents/unit-haproxy-5/charm/hooks/charmhelpers/fetch/__init__.py", line 169, in apt_cache
2016-07-01 17:13:20 INFO config-changed from apt import apt_pkg
2016-07-01 17:13:20 INFO config-changed ImportError: No module named apt
2016-07-01 17:13:20 ERROR juju.worker.uniter.operation runhook.go:107 hook "config-changed" failed: exit status 1

[James Jesudason (jamesj)]

This appears to be due to a missing package: python-apt

The simplest solution seems to be to include the installation of python-apt.

However, python3-apt *is* installed, but the hooks.py script is running as python2. However, additional changes will need to be made if the script is to run as python3.