anchor.diff:  { stdenv
   , buildPythonPackage
   , cython
  -, fetchFromGitHub
  -#, fetchPyPi
  +, fetchPyPi
   , isPy3
   , isPyPy
   , lib
  
positive.code:   inherit (lib)
      optionals;
  
    version = "2018-02-28";
    #version = "1.2.2";
  in
  buildPythonPackage rec {
    name = "gevent-${version}";
  
    # src = fetchPyPi {
    #   package = "gevent";
    #   inherit version;
    #   sha256 = "4791c8ae9c57d6f153354736e1ccab1e2baf6c8d9ae5a77a9ac90f41e2966b2d";
    # };
  
    # Switch back to stable releases once 1.3 is released.
    src = fetchFromGitHub {
      version = 5;
      owner = "gevent";
      repo = "gevent";
      rev = "a6844125377cdc7002166d9be00b17900674568a";
      sha256 = "596a86b94817100c0143bf9bd71c7a8003ec7abbfcfdc4ceed5f9a35232325fe";
    };
  
    nativeBuildInputs = [
  
negative.code:     "-I${greenlet}/include/${python.executable}${if isPy3 then "m" else ""}"
    ];
  
    meta = with lib; {
      description = "Coroutine-based networking library";
      homepage = http://www.gevent.org/;
  