Fix base Python dependencies.

Fix base Python dependencies.

The install hook imported charmhelpers
before installing python-yaml, and 
charmhelpers imports from yaml.

This very old bug has been hidden by the 
fact that python-yaml is automatically 
installed in ec2/lxc instances, but showed
itself when using the manual provider.

Copy/pasting and integrating the QA from 
my last branch, a double check can help
before the release.
QA:
- Bootstrap a Juju environment with --debug.
- Deploy and expose the GUI (make deploy).
- Check juju debug-log (or
  less ~/.juju/local/log/unit-juju-gui-0.log if you
  used lxc): you should see the following message
  at the beginning of the install hook log:
  "Installing base Python dependencies: python-apt, 
  python-launchpadlib, python-tempita, python-yaml."
- Wait for the GUI to be ready/started.
- Deploy this bundle: http://pastebin.ubuntu.com/6411548/
- Check everything is ok, xy annotations work (
  the services are vertically aligned), wordpress has
  customized constraints, mysql customized options and
  two units.
- No try to deploy the same bundle again, you
  will see a "services already there" kind of error.

https://code.launchpad.net/~frankban/charms/precise/juju-gui/install-yaml/+merge/195113

(do not edit description out of merge proposal)

[frankban, 2013-11-13 18:35:27]

Please take a look.

[frankban, 2013-11-13 18:37:50]

Please take a look.

[gary.poster, 2013-11-13 18:57:27]

LGTM and QAOK.  Thank you!

[frankban, 2013-11-13 19:03:37]

*** Submitted:

Fix base Python dependencies.

The install hook imported charmhelpers
before installing python-yaml, and 
charmhelpers imports from yaml.

This very old bug has been hidden by the 
fact that python-yaml is automatically 
installed in ec2/lxc instances, but showed
itself when using the manual provider.

Copy/pasting and integrating the QA from 
my last branch, a double check can help
before the release.
QA:
- Bootstrap a Juju environment with --debug.
- Deploy and expose the GUI (make deploy).
- Check juju debug-log (or
  less ~/.juju/local/log/unit-juju-gui-0.log if you
  used lxc): you should see the following message
  at the beginning of the install hook log:
  "Installing base Python dependencies: python-apt, 
  python-launchpadlib, python-tempita, python-yaml."
- Wait for the GUI to be ready/started.
- Deploy this bundle: http://pastebin.ubuntu.com/6411548/
- Check everything is ok, xy annotations work (
  the services are vertically aligned), wordpress has
  customized constraints, mysql customized options and
  two units.
- No try to deploy the same bundle again, you
  will see a "services already there" kind of error.

R=gary.poster
CC=
https://codereview.appspot.com/26190043