[Nix-dev] how to add buildInput with derivation

[Stefan Huchler]

Because I have problems with qutebrowser I want to try out the new
qtwebengine backend.

I am not 100% shure that I edit the right variable but I want to add
qtwebengine to the buildInputs variable of that package:

   {
     packageOverrides = pkgs: rec {
       qutebrowser = pkgs.stdenv.lib.overrideDerivation pkgs.qutebrowser (oldAttrs : {
         buildPythonApplication.buildInputs = [
           qtbase qtwebkit-plugins qtwebengine
           gst-plugins-base gst-plugins-good gst-plugins-bad gst-plugins-ugly gst-libav
           glib_networking
         ];
       });
     };
   }

I get then the error:

error: undefined variable ‘qtbase’ at /home/.../.nixpkgs/config.nix:5:12

here is the package I want to manipulate:

https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/networking/browsers/qutebrowser/default.nix

Can somebody give me a hint what I did wrong? And if that that would
work to get the qtwebengine backend availible?