MarsSeed [1] filed a deletion request for kast [2]: What this package offers sounds nice and convenient, but as an unmaintained orphan it's not useful to keep on AUR.
It has an upstream issue in setup requirements, preventing the packaging here. Without someone to take care of it, it is defunct. This module is available on PyPI, so maybe it's better to let it go from AUR. [1] https://aur.archlinux.org/account/MarsSeed/ [2] https://aur.archlinux.org/pkgbase/kast/
