anchor.diff:  , python
   , uvicorn
   , isPy27
  +, darwin
   }:
   
   buildPythonPackage rec {
  
positive.code: { lib
  , buildPythonPackage
  , fetchPypi
  , aiofiles
  
negative.code:     requests
      ujson
      uvicorn
    ] ++ stdenv.lib.optional stdenv.isDarwin [ darwin.apple_sdk.frameworks.ApplicationServices ];
  
    checkPhase = ''
      ${python.interpreter} -c """
  