Python's Six dependency

On trunk, charmhelpers/__init__.py detects that six is not installed and installs the python-six package with apt.

If your charmhelpers/__init__.py is empty, you managed to sync trunk when it was broken. Updating charm-helpers should fix your problem.

If the import code is in charmhelpers/__init__.py, then we need to understand why it is not being invoked as it was when we tested it.

We have recently been seeing this failure quite a bit for precise.

Seeing it for mysql and ceph charms primarily. Here's an excerpt from the unit-mysql-0.log of a failed build.

014-11-30 20:43:20 DEBUG juju.worker.uniter.charm manifest_deployer.go:126 preparing to deploy charm "local:precise/mysql-326"
2014-11-30 20:43:21 DEBUG juju.worker.uniter.charm manifest_deployer.go:102 deploying charm "local:precise/mysql-326"
2014-11-30 20:43:21 DEBUG juju.worker.uniter.charm manifest_deployer.go:147 finishing deploy of charm "local:precise/mysql-326"
2014-11-30 20:43:21 INFO juju.worker.uniter uniter.go:307 charm "local:precise/mysql-326" is deployed
2014-11-30 20:43:21 DEBUG juju.worker.uniter modes.go:398 ModeInstalling local:precise/mysql-326 exiting
2014-11-30 20:43:21 INFO juju.worker.uniter modes.go:396 ModeContinue starting
2014-11-30 20:43:21 INFO juju.worker.uniter modes.go:65 found queued "install" hook
2014-11-30 20:43:21 INFO juju.worker.uniter uniter.go:480 running "install" hook
2014-11-30 20:43:21 INFO install Traceback (most recent call last):
2014-11-30 20:43:21 INFO install File "/var/lib/juju/agents/unit-mysql-0/charm/hooks/install", line 6, in <module>
2014-11-30 20:43:21 INFO install import lib.utils as utils
2014-11-30 20:43:21 INFO install File "/var/lib/juju/agents/unit-mysql-0/charm/hooks/lib/utils.py", line 17, in <module>
2014-11-30 20:43:21 INFO install from charmhelpers.core.host import (
2014-11-30 20:43:21 INFO install File "/var/lib/juju/agents/unit-mysql-0/charm/hooks/charmhelpers/core/host.py", line 19, in <module>
2014-11-30 20:43:21 INFO install import six
2014-11-30 20:43:21 INFO install ImportError: No module named six
2014-11-30 20:43:21 ERROR juju.worker.uniter uniter.go:486 hook failed: exit status 1
2014-11-30 20:43:21 DEBUG juju.worker.uniter modes.go:398 ModeContinue exiting
2014-11-30 20:43:21 INFO juju.worker.uniter modes.go:396 ModeContinue starting
2014-11-30 20:43:21 INFO juju.worker.uniter modes.go:78 awaiting error resolution for "install" hook
2014-11-30 20:43:21 DEBUG juju.worker.uniter modes.go:398 ModeContinue exiting
2014-11-30 20:43:21 INFO juju.worker.uniter modes.go:396 ModeHookError starting

This all may be fixed on trunk. Per comment #2, I need to now if your version of charmhelpers/__init__.py is empty or not.

FYI, related bug on the mysql charm: https://bugs.launchpad.net/charms/+source/mysql/+bug/1398023

Bug #1398023 seems to have identified the problem, in a round about fashion.

charm-helpers-sync.py does not pull in charmhelpers/__init__.py unless you specifically ask for it. The work around for now is to add '__init__' to your charm-helpersyaml and resync:

branch: lp:charm-helpers
destination: hooks/charmhelpers
include:
    - __init__
    - core
    - fetch
    - contrib.network.ip

I doubt any existing charms would specify __init__.py, as it previously was empty. Many charms will not pick up the omission, as six is likely installed as a dependency already in their test environment. This will cause charms to fail when deployed to cleaner environments where six is not pulled in as a dependency.

The least annoying fix I can come up with is for charm-helpers-sync to implicitly sync charmhelpers/__init__.py. This way, charms will always get the bootstrap code and will find six and yaml available when it is needed (and I imagine this list of packages will expand over time)

Thanks for the fix!