anchor.diff:    name = "gnutls-3.1.12";
   
     src = fetchurl {
  -    url = "ftp://ftp.gnutls.org/gcrypt/gnutls/v3.1/${name}.tar.xz";
  -    sha256 = "025k37wsl21ncwrg489ysbjqsz8iralvgv98adj960sl03787lyc";
  +    url = "ftp://ftp.gnutls.org/gcrypt/gnutls/v3.1/${name}.tar.lz";
  +    sha256 = "1h8j3xi2jad2dclybgqffb5264hdqrxpsx99irs03yy9np6iw5l8";
     };
   
     # Note: GMP is a dependency of Nettle, whose public headers include
  
positive.code: { fetchurl, stdenv, zlib, lzo, libtasn1, nettle, pkgconfig
  , guileBindings, guile, perl, gmp }:
  
  assert guileBindings -> guile != null;
  
negative.code:   # http://hydra.nixos.org/build/2962084/nixlog/1/raw .
    doCheck = (!stdenv.isFreeBSD && !stdenv.isDarwin);
  
    meta = with stdenv.lib; {
      description = "The GNU Transport Layer Security Library";
  
      longDescription = ''
  