anchor.diff:  
   ### IMPORTANT: before updating cups, make sure the nixos/tests/printing.nix test
   ### works at least for your platform.
  -let version = "2.0.4"; in
  +let version = "2.1.3"; in
   
   with stdenv.lib;
   stdenv.mkDerivation {
  
positive.code:       # Work around a Makefile bug.
        "CUPS_PRIMARY_SYSTEM_GROUP=root"
      ];
  
    postInstall = ''
        # Delete obsolete stuff that conflicts with cups-filters.
  
negative.code: 
    src = fetchurl {
      url = "https://www.cups.org/software/${version}/cups-${version}-source.tar.bz2";
      sha256 = "1lyl3z01xhg9xb9c8m42398c6h9kw8qr6jwiv8bjdsjab11hv9rn";
    };
  
    buildInputs = [ pkgconfig zlib libjpeg libpng libtiff libusb gnutls libpaper ]
  