selinux: 2.9 -> 3.0 (#104087)

Notably, Python 2 code is not be supported in this project anymore and
new Python code should be written only for Python 3, which is no longer
restricted to Python 3.7 (see 780fb563c7,
5dfd3c4975)

https://github.com/SELinuxProject/selinux/releases/tag/20191204

pkgs/top-level/python-packages.nix

@@ -3447,13 +3447,13 @@ in {
       p.overrideAttrs (super: {
         meta = super.meta // {
           outputsToInstall = [ "py" ];
-          broken = (super.meta.broken or false) || pythonAtLeast "3.8";
+          broken = super.meta.broken or isPy27;
         };
       }))
     (p:
       p.override {
         enablePython = true;
-        inherit python;
+        python3 = python;
       })
     (p: p.py)
   ];