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