The python package set is for libraries only, packages that are only applications should be moved elsewhere in the tree. The openrazer library can stay in the package set and reuse the source from the application package, if necessary.

See https://github.com/NixOS/nixpkgs/blob/master/doc/languages-frameworks/python.section.md#buildpythonapplication-function-buildpythonapplication-function.

cc @evanjs @roelvandijk @Lucus16