This should save several minutes off the Travis CI `production`
suite's runtime, since previously we were doing the full apt upgrade
process twice, resulting in things like multiple expensive rebuilds of
the initramfs.
Travis CI's model of installing every version of postgres on the test
VM and then shutting all the versions other than the one requested
down seems to not work very well with doing apt upgrades. It seems
the best way to resolve this is to just uninstall the versions we
don't need.
We ran into a bug with the Travis CI infrastructure where it postgres
9.1 is installed on the system, and so when we'd do an apt upgrade
with a new version of 9.1, the 9.1 daemon would end up getting started
and conflict with the 9.3 daemon we were trying to run.
With this change, we are now testing the production static asset
pipeline and installation process in a new testing job (and also run
the frontend/backend tests separately).
This means that changes that break the Zulip static asset pipeline or
production installation process are more likely to fail tests. The
testing is imperfect in that it does not have proper isolation -- we
build a complete Zulip development environment and then install a
Zulip production environment on top of it, so e.g. any apt
dependencies installed for Zulip development will still be available
for the Zulip production environment. But, it's better than nothing!
A good v2 of this would be to have the production setup process just
install the minimum stuff needed to run `build-release-tarball` and
then uninstall it / clean it up so that we can do a more clear
production installation, but that's more work.
Tim Abbott