anchor.diff:  
     propagatedBuildInputs = [
       dateutil gflags httplib2 parsedatetime six vobject
  -    # overridden
       google_api_python_client oauth2client uritemplate
     ] ++ lib.optional (!isPy3k) futures;
   
  
positive.code: { stdenv, lib, fetchFromGitHub, python2
  , libnotify ? null }:
  
  let
    py = python2.override {
      packageOverrides = self: super: {
        google_api_python_client = super.google_api_python_client.overridePythonAttrs (oldAttrs: rec {
          version = "1.5.1";
          src = oldAttrs.src.override {
            inherit version;
            sha256 = "1ggxk094vqr4ia6yq7qcpa74b4x5cjd5mj74rq0xx9wp2jkrxmig";
          };
        });
  
        oauth2client = super.oauth2client.overridePythonAttrs (oldAttrs: rec {
          version = "1.4.12";
          src = oldAttrs.src.override {
            inherit version;
            sha256 = "0phfk6s8bgpap5xihdk1xv2lakdk1pb3rg6hp2wsg94hxcxnrakl";
          };
        });
  
        uritemplate = super.uritemplate.overridePythonAttrs (oldAttrs: rec {
          version = "0.6";
          src = oldAttrs.src.override {
            inherit version;
            sha256 = "1zapwg406vkwsirnzc6mwq9fac4az8brm6d9bp5xpgkyxc5263m3";
          };
          # there are no checks in this version
          doCheck = false;
        });
      };
    };
  
  in with py.pkgs; buildPythonApplication rec {
    version = "4.0.0a4";
    name = "gcalcli-${version}";
  
  
negative.code:   doCheck = false;
  
    meta = with lib; {
      description = "CLI for Google Calendar";
      homepage = https://github.com/insanum/gcalcli;
      license = licenses.mit;
      maintainers = with maintainers; [ nocoolnametom ];
      inherit version;
  