anchor.diff:  { stdenv, fetchurl, pkgconfig, dbus, glib, alsaLib,
  -  pythonPackages, readline, libsndfile, udev, libical,
  +  pythonPackages, readline, udev, libical,
     systemd, enableWiimote ? false }:
   
   assert stdenv.isLinux;
  
positive.code:   pythonPath = with pythonPackages;
      [ dbus pygobject2 pygobject3 recursivePthLoader ];
  
    buildInputs =
      [ pkgconfig dbus glib alsaLib pythonPackages.python pythonPackages.wrapPython
        readline libsndfile udev libical
        # Disables GStreamer; not clear what it gains us other than a
        # zillion extra dependencies.
        # gstreamer gst-plugins-base
      ];
  
    outputs = [ "out" "dev" "test" ];
  
  
negative.code:             list-devices \
              monitor-bluetooth \
              ; do
        ln -s ../test/$a $test/bin/bluez-$a
      done
      popd
      wrapPythonProgramsIn $test/test "$test/test $pythonPath"
  