I think the safest thing to do (and this is oversimplifying) is:
return 'xenial';
Why? Because we have no way of knowing whether or not our commissioning scripts will work on any other LTS. They're only well-tested on Xenial. When the next LTS arrives, along with it will come a version of MAAS that has been tested with LTS-next. At which time we would re-test our commissioning scripts with LTS-next and change the hard-coded release.
When LTS-next arrives, current MAAS 2.2 users might break if we suddenly change commissioning to use LTS-next.
We should have a way to override this so that we can CI-test commissioning with development releases.
I think the safest thing to do (and this is oversimplifying) is:
return 'xenial';
Why? Because we have no way of knowing whether or not our commissioning scripts will work on any other LTS. They're only well-tested on Xenial. When the next LTS arrives, along with it will come a version of MAAS that has been tested with LTS-next. At which time we would re-test our commissioning scripts with LTS-next and change the hard-coded release.
When LTS-next arrives, current MAAS 2.2 users might break if we suddenly change commissioning to use LTS-next.
We should have a way to override this so that we can CI-test commissioning with development releases.