anchor.diff:    , buildPythonPackage
     , isPy3k
     , pythonOlder
  +  , pythonAtLeast
     , fetchFromGitHub
     , pyparsing
     , opencascade
  
positive.code: in
    buildPythonPackage rec {
      pname = "cadquery";
      version = "2.0RC0";
    
      src = fetchFromGitHub {
        owner = "CadQuery";
        repo = pname;
        rev = version;
        sha256 = "1xgd00rih0gjcnlrf9s6r5a7ypjkzgf2xij2b6436i76h89wmir3";
      };
    
      buildInputs = [
        opencascade
      ];
    
      propagatedBuildInputs = [
        pyparsing
        pythonocc-core-cadquery
      ];
    
      # Build errors on 2.7 and >=3.8 (officially only supports 3.6 and 3.7).
      disabled = !(isPy3k && (pythonOlder "3.8"));
    
      meta = with lib; {
        description = "Parametric scripting language for creating and traversing CAD models";
        homepage = "https://github.com/CadQuery/cadquery";
  
negative.code:   , libGLU
    , libX11
    , six
    , pytest
    , makeFontsConf
    , freefont_ttf
  }:
  
  let
    pythonocc-core-cadquery = stdenv.mkDerivation {
      pname = "pythonocc-core-cadquery";
      version = "0.18.2";
  