anchor.diff:      maintainers = [ maintainers.kiwi ];
     };
   }
  -
  
positive.code:   propagatedBuildInputs = [ defusedxml lxml ];
  
    postPatch = ''
      substituteInPlace requirements/test.txt \
         --replace "pytest >= 3.6.0, < 4.1.0" "pytest >= 4.2.1, < 5"
    '';
  
    preBuild = ''
  
negative.code: 
  buildPythonPackage rec {
    pname = "pikepdf";
    version = "1.6.2";
    disabled = ! isPy3k;
  
    src = fetchPypi {
      inherit pname version;
      sha256 = "1x1b55znr0j4fib69l2h0xq0qmbf2nbxwbwd4f7y8r4sqi20239z";
    };
  
    buildInputs = [
  