Comment 73 for bug 1267393

On Mon, Sep 28, 2015 at 07:51:47AM -0000, Tim Penhey wrote:
> > It is currently impossible to upgrade from 14.04 LTS to 15.04 due to
> > incorrect version numbers. Has anyone else noticed this yet? When will
> > this be fixed? Are there any changes in process needed to ensure this
> > doesn't happen in the future?
> [...]
> We do test a number of upgrade combinations, and I'm curious as to why
> you say it is impossible to upgrade? What exactly is the situation you
> are attempting?

In short, install trusty, install juju, apt-get update && apt-get -u
dist-upgrade; then, use do-release-upgrade to upgrade from trusty to
vivid. This upgrade will fail and uninstalling juju will be the easiest
path forward for the administrator.

I filed https://bugs.launchpad.net/ubuntu/+source/juju-core/+bug/1497087
for this bug.

The Debian tool piuparts is one way to do automated testing for this case,
it might be worth bringing it over to Ubuntu; in the meantime, teams need
to be aware to make sure that version numbers in supported releases always
allow upgrades.

Thanks