anchor.diff:      pypdf2
       dict2xml
       weasyprint
  +    ConfigArgParse
  +    appdirs
     ];
   
     preCheck = ''
  
positive.code: 
    # lxml tries to fetch from the internet
    doCheck = false;
  
    meta = with lib; {
      description = "Tool generating IETF RFCs and drafts from XML sources";
      homepage = "https://tools.ietf.org/tools/xml2rfc/trac/";
      # Well, parts might be considered unfree, if being strict; see:
  
negative.code: { stdenv, fetchPypi, buildPythonPackage, pythonAtLeast, intervaltree, pyflakes, requests, lxml, google-i18n-address
  , pycountry, html5lib, six, kitchen, pypdf2, dict2xml, weasyprint, pyyaml, jinja2, ConfigArgParse, appdirs
  }:
  
  buildPythonPackage rec {
    pname = "xml2rfc";
    version = "3.5.0";
    disabled = pythonAtLeast "3.9";
  
    src = fetchPypi {
      inherit pname version;
  