It has become impractical to maintain support for the latest production releases on Ubuntu Trusty 14.04LTS due to behaviour required by the server side changes needed by the dispatcher refactoring. These are important changes and are impractical to backport to the version of python-django available in Trusty.
I have tried working around the issues but it involves pulling more dependencies from Jessie or Vivid and in my tests, the existing installation became confused and failed to install due to problems with the database migrations. The LAVA software team do not have the resources to maintain backports of the complete dependency chain in Ubuntu, it is a much more manageable set in Debian Jessie (where the same migration went without issues on multiple machines).
The changes in 2015.11 are almost exclusively related to the dispatcher refactoring and therefore there is expected to be limited impact on current installations on Trusty.
For the next release, we will investigate code changes which omit the new support for Trusty builds but this will have the effect of preventing those installs from working with the pipeline and the new YAML job submissions. The documentation for Trusty will also be updated, if necessary as a hotfix to 2015.9 just for Trusty.
If the code changes do not work cleanly, then the current 2015.9 (and the documentation hotfix to follow) would become the last LAVA releases for Ubuntu Trusty 14.04LTS.
Users of Ubuntu Trusty 14.04LTS are reminded that a new LTS is due for release in April 2016 but that the LAVA software team are not using Trusty any longer. Any issues with the migration from Trusty to the new LTS are outside of our control.
Migrating an instance from Ubuntu to Debian would involve dumping and re-importing the database - bear in mind that Trusty has postgres9.3 and Jessie has 9.4, so care will be needed to migrate the postgresql cluster correctly - there is documentation for that migration in the lava-server docs. It is not recommended to attempt to migrate the OS itself from Ubuntu to Debian (or vice-versa), a reinstall is a better option, so make a backup and ensure that the backup works.