python-nixpart: Add Hetzner-specific attribute.

This is for NixOps and the corresponding Hetzner backend and allows for easy
referencing by nix-build using the -A argument.

Basically the Hetzner rescue system uses an older udev version from Debian, so
we need to use shared object major number 0 here.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

pkgs/top-level/python-packages.nix

@@ -66,6 +66,10 @@ pythonPackages = python.modules // rec {
   });
 
   nixpart = callPackage ../tools/filesystems/nixpart { };
+  nixpartHetzner = nixpart.override {
+    useNixUdev = false;
+    udevSoMajor = 0;
+  };
 
   pil = import ../development/python-modules/pil {
     inherit (pkgs) fetchurl stdenv libjpeg zlib freetype;