Comment 6 for bug 1943292

One obstacle I found is that we need to port from bzr-builder to brz-builder in order to be able to build VM images for focal, since that's used by source package recipe builds. I've prepared suitable packaging in https://code.launchpad.net/~launchpad/+recipe/brz-builder-daily (it all gets a bit meta), though launchpad-buildd will also need a small change to make use of this.