anchor.diff:  , buildPythonPackage
   , fetchFromGitHub
   , fsspec
  -, pytest
  +, pytestCheckHook
   , pythonOlder
   , cloudpickle
   , numpy
  
positive.code:       --replace "cmdclass=versioneer.get_cmdclass()," ""
    '';
  
    checkPhase = ''
      pytest
    '';
  
    meta = {
      description = "Minimal task scheduling abstraction";
  
negative.code: 
  buildPythonPackage rec {
    pname = "dask";
    version = "2.14.0";
  
    disabled = pythonOlder "3.5";
  
  