Bug#945858: b-d on python3-all-dev, but not built for all supported Python3 versions

[Sebastien Bacher]

Package: libplist
Version: 2.0.1~git20190104.3f96731-1

The package build-depends on python3-all-dev, but does not build for all
supported python3 versions, it should rather b-d on python3-dev if it
only needs to build with the current python version