Comment 5 for bug 1657825

Before enforcing this on some classic snaps, please fix https://forum.snapcraft.io/t/launchpad-post-build-pre-upload-testing/5545 first. For now I've taken Launchpad builds out of git-ubuntu's publication pipeline since we were hitting non-deterministic bad snap builds which, while detectable, cannot currently be blocked from publication by Launchpad since there currently exists no hook for Launchpad to be able to test produced snaps.