anchor.diff:    inherit buildInputs;
     C_INCLUDE_PATH = concatStringsSep ":" (map (p: "${p}/include") buildInputs);
     LIBRARY_PATH = concatStringsSep ":" (map (p: "${p}/lib") buildInputs);
  -  configureFlags = ''${if stdenv.isDarwin then "" else " --enable-shared"} --with-wctype-functions'';
  +  configureFlags = ''${if stdenv.isDarwin then "" else " --enable-shared"} --with-threads --enable-unicode --with-wctype-functions'';
   
     preConfigure = ''
       # Purity.
  
positive.code: in
  
  stdenv.mkDerivation ( {
    name = "python-2.6.3";
  
    src = fetchurl {
      url = http://www.python.org/ftp/python/2.6.3/Python-2.6.3.tar.bz2;
      sha256 = "096wxhibhss3clgcj5n3xx5wmdsqmywk3h3bp68sicp7sy4y6rs3";
    };
  
    patches = [
  
negative.code: 
  let
  
    majorVersion = "2.6";
    version = "${majorVersion}.4";
  
    buildInputs =
      optional (stdenv ? gcc && stdenv.gcc.libc != null) stdenv.gcc.libc ++
      [bzip2]
  