anchor.diff:  
   buildPythonPackage rec {
     pname = "python-language-server";
  -  version = "0.28.3";
  +  version = "0.29.1";
   
     src = fetchFromGitHub {
       owner = "palantir";
       repo = "python-language-server";
       rev = version;
  -    sha256 = "16d8i43r75h0cijggkkmmpnycn29wlbjp63mgg3s4nbrxfa96x2k";
  +    sha256 = "0hsp0h8vma8z6f0mg311hp59h6hayl7zzxmy295x5fl2l9iiakfv";
     };
   
     # The tests require all the providers, disable otherwise.
  
positive.code:     HOME=$TEMPDIR pytest
    '';
  
    propagatedBuildInputs = [ setuptools jedi pluggy future python-jsonrpc-server ]
      ++ stdenv.lib.optional (withProvider "autopep8") autopep8
      ++ stdenv.lib.optional (withProvider "mccabe") mccabe
      ++ stdenv.lib.optional (withProvider "pycodestyle") pycodestyle
  
negative.code: { stdenv, buildPythonPackage, fetchFromGitHub, pythonOlder, isPy27
  , backports_functools_lru_cache, configparser, futures, future, jedi, pluggy, python-jsonrpc-server, flake8
  , pytest, mock, pytestcov, coverage, setuptools
  , # Allow building a limited set of providers, e.g. ["pycodestyle"].
    providers ? ["*"]
  