anchor.diff:  
   # http://sources.gentoo.org/cgi-bin/viewvc.cgi/gentoo-x86/gnome-base/gnome-shell/gnome-shell-3.10.2.1.ebuild?revision=1.3&view=markup
   
  -stdenv.mkDerivation rec {
  +let
  +  pythonEnv = python3Packages.python.withPackages ( ps: with ps; [ pygobject3 ] );
  +in stdenv.mkDerivation rec {
     inherit (import ./src.nix fetchurl) name src;
   
     # Needed to find /etc/NetworkManager/VPN
  
positive.code:       defaultIconTheme sqlite gnome3.gnome-bluetooth
        libgweather # not declared at build time, but typelib is needed at runtime
        gnome3.gnome-clocks # schemas needed
        at_spi2_core upower ibus gnome_desktop telepathy_logger gnome3.gnome_settings_daemon ];
  
    propagatedBuildInputs = [ python3Packages.pygobject3 python3Packages.python gobjectIntrospection ];
  
    installFlags = [ "keysdir=$(out)/share/gnome-control-center/keybindings" ];
  
  
negative.code:       --set GDK_PIXBUF_MODULE_FILE "$GDK_PIXBUF_MODULE_FILE" \
        --prefix XDG_DATA_DIRS : "${gnome_themes_standard}/share:$out/share:$XDG_ICON_DIRS" \
        --suffix XDG_DATA_DIRS : "$GSETTINGS_SCHEMAS_PATH"
  
      wrapProgram "$out/libexec/gnome-shell-calendar-server" \
        --prefix XDG_DATA_DIRS : "${evolution_data_server}/share:$out/share:$XDG_ICON_DIRS:$GSETTINGS_SCHEMAS_PATH"
  