pytest-forked removed support for python2 in their 1.4.0 release,
breaking the pinned version of mutagen that the old version of
spotify-ripper requires. We rebase onto another fork that has updated it
a bit, adding support for python3 and unpinning their dependencies.
This commit moves a lot of the heavy lifting out of callPackage and back
into regular import, following conventions from upstream Nixpkgs. It
allows for a clearer and less magic definition of new packages,
particularly by downstream, as well, by exposing the *Build package
callers in the attribute set.
