The 'master' branch of MediaWiki-Vagrant will now provision and maintain Debian Jessie based VMs. The next time you fetch mediawiki/vagrant.git changes to your laptop or Labs VM and try to run `vagrant up` or `vagrant provision` it will complain that your Vagrant managed VM is not running the correct base operating system.
There are two ways to deal with this:
1) Follow the instructions given to delete and recreate your VM. This is the most awesome long term thing to do, but may be annoying in the short term. If you have heavily customized the wikis running in your VM it is up to you to figure out how to backup things before you destroy your current VM and then restore the changes after you build a new Jessie-based VM.
2) Switch your git checkout to the 'trusty-compat' branch of mediawiki/vagrant.git. This trades short term efficiency for long term pain. The trusty-compat branch is not going away any time soon, but it will drift out of sync with Puppet changes on the master branch.
See https://phabricator.wikimedia.org/T136429 for known issues with the Jessie conversion. The only two I'm aware of at this time are related to fundraising (T154264) and an NFS permissions mapping problem when installing ChangeProp on a VM with OSX as the host operating system and NFS shares enabled for Vagrant (T158617).
Bryan