anchor.diff:          inherit pythonEnv;
           inherit sage-src openblas-blas-pc openblas-cblas-pc openblas-lapack-pc pynac singular;
           pkg-config = nixpkgs.pkgconfig; # not to confuse with pythonPackages.pkgconfig
  -        three = nodePackages_8_x.three;
  +        three = nodePackages.three;
         };
   
         sage = self.callPackage ./sage.nix { };
  
positive.code: }:
  
  let
    inherit (nixpkgs) fetchpatch fetchurl symlinkJoin callPackage nodePackages_8_x;
  
    # https://trac.sagemath.org/ticket/15980 for tracking of python3 support
    python = nixpkgs.python2.override {
  
negative.code:       env-locations = self.callPackage ./env-locations.nix {
          inherit pari_data ecl;
          inherit singular;
          three = nodePackages.three;
          mathjax = nodePackages.mathjax;
        };
  
        sage-env = self.callPackage ./sage-env.nix {
  