anchor.diff:    src = fetchPyPi {
       package = "aniso8601";
       inherit version;
  -    sha256 = "4fc462db59811f541bc25d865b86367153d8ce773ae75b16d54e2e1cd393b5cc";
  +    sha256 = "e7ba4f42d3aea75909c79b1f4c4614768b4f13fbb98fc658a7b6061ddb0be47c";
     };
   
     propagatedBuildInputs = [
  
positive.code: 
    doCheck = true;
  
    meta = with stdenv.lib; {
      description = "A library for parsing ISO 8601 strings";
      homepage = https://bitbucket.org/nielsenb/aniso8601;
      license = licenses.bsd3;
  
negative.code: { stdenv
  , buildPythonPackage
  , fetchPyPi
  , lib
  
  , python-dateutil
  }:
  
  let
    version = "1.2.1";
  in
  buildPythonPackage rec {
    name = "aniso8601-${version}";
  