I'd prefer to have this still be None and have the appender on the other side be smart enough to create the file if needed.

The main reason is that I think this *may* conflict with the autodiscovered maintainer-script feature whereby adding scripts in `src/debian/DEBIAN` are automatically picked up by the build.  I'd like to run a quick test to see what happens there.

Also, if you have any suggestions for how to automate testing created DEB files, let me know.  I want to try to get automated tests for these postinst/preinst script things we're doing but so far I haven't found  a good mechanism.