anchor.diff:      proj
       protobufc
       zlib
  -  ] ++ lib.optional withPython python2;
  +  ] ++ lib.optional withPython python3;
   
     cmakeFlags = [
       "-DWITH_KML=ON"
  
positive.code: { lib, stdenv, fetchFromGitHub, cmake, pkg-config
  , cairo, curl, fcgi, freetype, fribidi, gdal, geos, giflib, harfbuzz
  , libjpeg, libpng, librsvg, libxml2, postgresql, proj, protobufc, zlib
  , withPython ? true, swig, python2
  }:
  
  stdenv.mkDerivation rec {
  
negative.code:   nativeBuildInputs = [
      cmake
      pkg-config
    ] ++ lib.optional withPython [ swig python3.pkgs.setuptools ];
  
    buildInputs = [
      cairo
  