anchor.diff:        --prefix PATH : "${ffmpeg}/bin"
     '';
   
  -  # Requires network
  +  # Tests requires network access
     doCheck = false;
  +
  +  passthru = {
  +    srcVerification = fetchurl rec {
  +      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";
  +    };
  +  };
   
     meta = with stdenv.lib; {
       description = "CLI tool to download videos from YouTube.com & other sites";
  
positive.code: , zip
  }:
  
  let
    inherit (stdenv.lib)
      optionalString;
  in
  
  # Pandoc is required to build the package's man page. Release tarballs
  # contain a formatted man page already, though, so it's fine to pass
  # "pandoc = null" to this derivation; the man page will still be
  
negative.code: # case someone wants to use this derivation to build a Git version of
  # the tool that doesn't have the formatted man page included.
  
  let
    inherit (stdenv.lib)
      optionalString;
  
    version = "2016.08.07";
  in
  buildPythonPackage rec {
    name = "youtube-dl-${version}";
  
    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";
      allowHashOutput = false;
      sha256 = "6f42477c562291cd392b7a034a7b828bbf1e209a48de7629848ba82a3aacdc1f";
    };
  
    nativeBuildInputs = [
  