Code review comment for lp:~jjo/charms/precise/postgresql/support-no-explicit-version_and_trusty-pg93

I don't think allowing an unspecified PostgreSQL version is a good idea. It means charm deployment is not repeatable, as which version is deployed depends on the state of the archive. I don't want 9.4 (or worse, 9.4 beta) being installed when my apps are tested with 9.3 just because a newer version is available in the archive. This would also break replication, as a unit does not know what version the other units in the service are using until after the install hook is run and the unit attempt's to join the service's peer relation. Archives will not always be under user control, in particular apt.postgresql.org for official Debian and Ubuntu backports.

If we really need this so the default version under trusty is 9.3, and the default version under precise is 9.1, I think we just want to check 'lsb_release -sc' and hard code the default version to the codename. This may still cause surprises, but would be repeatable.

If we keep the 'apt' import, do we need to add python-apt to the default list of packages to install?