anchor.diff:    src = fetchurl {
       url = "https://github.com/rg3/youtube-dl/releases/download/"
         + "${version}/${name}.tar.gz";
  -    sha512Url = "https://github.com/rg3/youtube-dl/releases/download/"
  -      + "${version}/SHA2-512SUMS";
       hashOutput = false;
  -    sha256 = "6cdeb0876295bef0325b8433c47c1ed13ebab3b108ef5ee27171e06b6958cb35";
  +    sha256 = "ed8d4a247c4cfffe2a1171b4f9c20be19e84d96bcf3716f46988c8503b1b7713";
     };
   
     nativeBuildInputs = [
  
positive.code:       inherit (src)
          outputHash
          outputHashAlgo
          sha512Urls
          urls;
        failEarly = true;
        pgpsigUrls = map (n: "${n}.sig") src.urls;
        pgpKeyFingerprint = "ED7F 5BF4 6B3B BED8 1C87  368E 2C39 3E0F 18A9 236D";
      };
    };
  
  
negative.code:   inherit (stdenv.lib)
      optionalString;
  
    version = "2016.10.19";
  in
  buildPythonPackage rec {
    name = "youtube-dl-${version}";
  