anchor.diff:  { lib
  -, fetchPypi
   , buildPythonPackage
  +, fetchFromGitHub
   , pythonOlder
   , intervaltree
   , pyflakes
  
positive.code: , jinja2
  , configargparse
  , appdirs
  }:
  
  buildPythonPackage rec {
    pname = "xml2rfc";
    version = "3.12.3";
  
    disabled = pythonOlder "3.6";
  
    src = fetchPypi {
      inherit pname version;
      sha256 = "sha256-YUrcD3Q1fkDW+nwf6k2T/aBL8+W9iWkPYW/TqdTiuA0=";
    };
  
    propagatedBuildInputs = [
      intervaltree
  
negative.code:     appdirs
    ];
  
    checkInputs = [
      decorator
      pycairo
      pytestCheckHook
      python-fontconfig
    ];
  
     # requires Noto Serif and Roboto Mono font
    doCheck = false;
  
    checkPhase = ''
      make tests-no-network
    '';
  
    pythonImportsCheck = [ "xml2rfc" ];
  
    meta = with lib; {
      description = "Tool generating IETF RFCs and drafts from XML sources";
      homepage = "https://github.com/ietf-tools/xml2rfc";
      # Well, parts might be considered unfree, if being strict; see:
      # http://metadata.ftp-master.debian.org/changelogs/non-free/x/xml2rfc/xml2rfc_2.9.6-1_copyright
      license = licenses.bsd3;
  