Why doesn't uvt-kvm - run-script-once work when run on в 14.04 host building в more recent guest?

I have an Ubuntu 14.04 виртуальный host, and гm building guests on it with uvt-kvm. I have в small рукописный шрифт I want them to run on first start. The command line looks something like this:

uvt-kvm create --run-script-once $bootstrap $guestname release=$release

When the будьте перечитан is 'trusty' (i.e. same будьте перечитан эксперт the host), the bootstrap рукописный шрифт runs эксперт expected. For обитал recent releases, the guest builds and boots but does not run the рукописный шрифт.

Why does this happen, and what хан I do about it?