I am looking for a script that automates the conversion of a Debian apt-package including dependencies to a snap package for ubuntu core/touch?
This script was a good one, however, it's aging and not supported anymore. The good news is that you have easier way now with snapcraft to do it!
Basically, you have snapcraft parts, and you can attach to them some
stage-packages that will download your deb from the Ubuntu repo (ppa support is in progress). The resulting binary will be put in the snapcraft stage directoy.
I encourage you to have a look at this page (section "Adding an Ubuntu dependency to a part"): https://developer.ubuntu.com/en/snappy/build-apps/your-first-snap/ where you can see that
fswebcam is pulled from the upstream repository, and then, have a look at the snapcraft tutorial: https://developer.ubuntu.com/en/snappy/build-apps/get-started/