anchor.diff:  { stdenv, fetchFromGitHub, writeScript, glibcLocales
  -, pythonPackages, imagemagick
  +, python2Packages, imagemagick
   
   , enableAcousticbrainz ? true
   , enableAcoustid       ? true
  
positive.code: , bashInteractive, bash-completion
  }:
  
  assert enableAcoustid    -> pythonPackages.pyacoustid     != null;
  assert enableBadfiles    -> flac != null && mp3val != null;
  assert enableConvert     -> ffmpeg != null;
  assert enableDiscogs     -> pythonPackages.discogs_client != null;
  assert enableFetchart    -> pythonPackages.responses      != null;
  assert enableKeyfinder   -> keyfinder-cli != null;
  assert enableLastfm      -> pythonPackages.pylast         != null;
  assert enableMpd         -> pythonPackages.mpd            != null;
  assert enableReplaygain  -> bs1770gain                    != null;
  assert enableThumbnails  -> pythonPackages.pyxdg          != null;
  assert enableWeb         -> pythonPackages.flask          != null;
  
  with stdenv.lib;
  
  
negative.code:   testShell = "${bashInteractive}/bin/bash --norc";
    completion = "${bash-completion}/share/bash-completion/bash_completion";
  
  in python2Packages.buildPythonApplication rec {
    name = "beets-${version}";
    version = "1.3.19";
  
  