We don't *really* need it in our builders, it's more useful for "real"
VMs to identify who's who and where...

This, at least, is the current username in bookworm, maybe it changed?

It was getting quite unwieldy, with
cowbuilder/pbuilder/sbuild/schroot/qemu instructions all over the
place. Now we clearly outline the schroot/qemu instructions
separately, and we've taken the VM disgression out into the blog post.