anchor.diff: -{ buildPythonPackage
  -, lib
  +{ lib
  +, buildPythonPackage
   , isPy27
   , nixosTests
   , fetchPypi
  
positive.code:   '';
  
    checkInputs = [
      flask_testing
      pytestCheckHook
    ];
  
    pythonImportsCheck = [ "ihatemoney" ];
  
    disabledTests = [
      "test_notifications"  # requires running service.
      "test_invite"         # requires running service.
      "test_invitation_email_failure" # requires dns resolution
    ];
  
    passthru.tests = {
  
negative.code: , werkzeug
  , wtforms
  , psycopg2 # optional, for postgresql support
  , flask-testing
  , pytestCheckHook
  , fetchpatch
  }:
  