anchor.diff:  , enableBadfiles   ? true, flac ? null, mp3val ? null
   , enableDiscogs    ? true
   , enableEchonest   ? true
  +, enableEmbyupdate ? true
   , enableFetchart   ? true
   , enableLastfm     ? true
   , enableMpd        ? true
  
positive.code:     chroma = enableAcoustid;
      discogs = enableDiscogs;
      echonest = enableEchonest;
      fetchart = enableFetchart;
      lastgenre = enableLastfm;
      lastimport = enableLastfm;
  
negative.code:     pythonPackages.unidecode
      python.modules.sqlite3
      python.modules.readline
    ] ++ optional enableAcoustid     pythonPackages.pyacoustid
      ++ optional (enableFetchart
                || enableEmbyupdate) pythonPackages.requests2
      ++ optional enableDiscogs      pythonPackages.discogs_client
      ++ optional enableEchonest     pythonPackages.pyechonest
      ++ optional enableLastfm       pythonPackages.pylast
      ++ optional enableMpd          pythonPackages.mpd
      ++ optional enableThumbnails   pythonPackages.pyxdg
      ++ optional enableWeb          pythonPackages.flask
      ++ optional enableAlternatives (import ./alternatives-plugin.nix {
        inherit stdenv buildPythonPackage pythonPackages fetchFromGitHub;
      });
  