anchor.diff:  buildPythonPackage rec {
     pname = "pymemcache";
     version = "3.5.1";
  +  format = "setuptools";
   
     src = fetchFromGitHub {
       owner = "pinterest";
  
positive.code:     rev = "v${version}";
      sha256 = "sha256-DKqfv5gf9gzbnEPQSzy2mAaVYJZL9jmTKyGWVzj40T4=";
    };
  
    checkInputs = [
      future
  
negative.code: { lib
  , buildPythonPackage
  , fetchFromGitHub
  , six
  , future
  , mock
  , pytestCheckHook
  