anchor.diff:  
     src = fetchurl {
       url = "https://github.com/tvheadend/tvheadend/archive/v${version}.tar.gz";
  -    sha256 = "05jidg7jma3mban40iy1bg3sirw6crscxkd8b70if4kjlf86i31l";
  +    sha256 = "0vhj4vkgl4brjw1pdc80g1wbjn6hyy57jrxkwilnivqfd1mwx3aw";
     };
   
     enableParallelBuilding = true;
  
positive.code: {avahi, dbus, fetchurl, git, gzip, libav, libiconv, openssl, pkgconfig, python
  , stdenv, which, zlib}:
  
  with stdenv.lib;
  
  let version = "4.0.6";
      pkgName = "tvheadend";
  
  in
  
negative.code:   # cannot happen during build.
    configureFlags = [ "--disable-dvbscan" ];
  
    buildInputs = [ avahi dbus git gnutar gzip libav libiconv openssl pkgconfig python
      which zlib ];
  
    preConfigure = ''
      patchShebangs ./configure
      substituteInPlace src/config.c --replace /usr/bin/tar ${gnutar}/bin/tar
    '';
  
    meta = {
      description = "TV steaming server";
  