anchor.diff:    buildInputs = [ pytestrunner ];
     checkInputs = [
       email_validator
  +    freezegun
       mock
  +    more-itertools
  +    pytest
  +    random2
       ukpostcodeparser
  -    pytest
     ];
   
     propagatedBuildInputs = [
  
positive.code: { lib, buildPythonPackage, fetchPypi, pythonOlder,
    # Build inputs
    dateutil, six, text-unidecode, ipaddress ? null,
    # Test inputs
    email_validator, mock, ukpostcodeparser, pytestrunner, pytest}:
  
  assert pythonOlder "3.3" -> ipaddress != null;
  
  
negative.code:   ] ++ lib.optional (pythonOlder "3.3") ipaddress;
  
    postPatch = ''
      substituteInPlace setup.py --replace "pytest>=3.8.0,<3.9" "pytest"
  
      # see https://github.com/joke2k/faker/pull/911, fine since we pin correct
      # versions for python2
      substituteInPlace setup.py --replace "more-itertools<6.0.0" "more-itertools"
    '';
  
    meta = with lib; {
  