anchor.diff:    };
     nativeBuildInputs = [ cmake pkg-config makeWrapper ];
     buildInputs = [
  -    boost_static guile eigen libpng python
  +    boost_static guile eigen libpng python3
       libGLU qt4 openexr openimageio opencolorio_1 xercesc
       osl seexpr
     ];
  
positive.code: { lib, stdenv, fetchFromGitHub, cmake, boost165, pkg-config, guile,
  eigen, libpng, python, libGLU, qt4, openexr, openimageio,
  opencolorio_1, xercesc, ilmbase, osl, seexpr, makeWrapper
  }:
  
  let boost_static = boost165.override {
    enableStatic = true;
    enablePython = true;
  };
  in stdenv.mkDerivation rec {
  
  
negative.code:   # Work around a bug in the CMake build:
    postInstall = ''
      chmod a+x $out/bin/*
      wrapProgram $out/bin/appleseed.studio --set PYTHONHOME ${python3}
    '';
  }
  
  