anchor.diff:  
     outputs = [ "out" "dev" ];
   
  -  nativeBuildInputs = [ cython pkgconfig ]
  -                    ++ stdenv.lib.optional stdenv.isDarwin darwin.cctools;
  +  nativeBuildInputs = [ cython pkg-config ]
  +    ++ stdenv.lib.optional stdenv.isDarwin darwin.cctools;
   
     buildInputs = [ c-ares openssl zlib ];
     propagatedBuildInputs = [ six protobuf ]
  -                        ++ stdenv.lib.optionals (isPy27) [ enum34 futures ];
  +    ++ stdenv.lib.optionals (isPy27) [ enum34 futures ];
   
     preBuild = stdenv.lib.optionalString stdenv.isDarwin "unset AR";
   
  
positive.code:   GRPC_PYTHON_BUILD_SYSTEM_ZLIB = 1;
    GRPC_PYTHON_BUILD_SYSTEM_CARES = 1;
  
    meta = with stdenv.lib; {
      description = "HTTP/2-based RPC framework";
      license = licenses.asl20;
      homepage = "https://grpc.io/grpc/python/";
      maintainers = with maintainers; [ ];
    };
  }
  
negative.code: { stdenv
  , buildPythonPackage
  , darwin
  , grpc
  , six
  , protobuf
  , enum34
  , futures
  , isPy27
  , pkg-config
  , cython
  , c-ares
  , openssl
  , zlib
  }:
  
  buildPythonPackage rec {
    inherit (grpc) src version;
  