anchor.diff:  
     doCheck = !stdenv.isDarwin;
   
  +  pythonImportsCheck = [ "dulwich" ];
  +
     meta = with lib; {
       description = "Simple Python implementation of the Git file formats and protocols";
       longDescription = ''
  
positive.code:     '';
      homepage = "https://www.dulwich.io/";
      changelog = "https://github.com/dulwich/dulwich/blob/dulwich-${version}/NEWS";
      license = with licenses; [ asl20 gpl2Plus];
      maintainers = with maintainers; [ koral ];
    };
  }
  
negative.code: { lib
  , stdenv
  , buildPythonPackage
  , certifi
  , fastimport
  , fetchPypi
  , gevent
  , geventhttpclient
  , git
  , glibcLocales
  , mock
  , urllib3
  }:
  
  buildPythonPackage rec {
    version = "0.20.18";
    pname = "dulwich";
  
    src = fetchPypi {
      inherit pname version;
      sha256 = "sha256-ATE4f5uZrsxprJhlWzkx8q1D2lPTpj4FD6Om1iYKxVQ=";
    };
  
    LC_ALL = "en_US.UTF-8";
  