anchor.diff: -{ stdenv, fetchFromGitHub, writeScript
  +{ stdenv, fetchFromGitHub, writeScript, glibcLocales
   , buildPythonPackage, pythonPackages, python
   
   , enableAcoustid   ? true
  -, enableBeatport   ? true
   , enableDiscogs    ? true
   , enableEchonest   ? true
   , enableFetchart   ? true
   , enableLastfm     ? true
   , enableMpd        ? true
   , enableReplaygain ? true
  +, enableThumbnails ? true
   , enableWeb        ? true
   
   , bashInteractive, bashCompletion
   }:
   
   assert enableAcoustid    -> pythonPackages.pyacoustid     != null;
  -assert enableBeatport    -> pythonPackages.responses      != null;
   assert enableDiscogs     -> pythonPackages.discogs_client != null;
   assert enableEchonest    -> pythonPackages.pyechonest     != null;
   assert enableFetchart    -> pythonPackages.responses      != null;
   assert enableLastfm      -> pythonPackages.pylast         != null;
   assert enableMpd         -> pythonPackages.mpd            != null;
  +assert enableThumbnails  -> pythonPackages.pyxdg          != null;
   assert enableReplaygain  -> pythonPackages.audiotools     != null;
   assert enableWeb         -> pythonPackages.flask          != null;
   
  
positive.code: 
  in buildPythonPackage rec {
    name = "beets-${version}";
    version = "1.3.10";
    namePrefix = "";
  
    src = fetchFromGitHub {
      owner = "sampsyo";
      repo = "beets";
      rev = "v${version}";
      sha256 = "136rvzpygjym6hxq19qwiri5jxx718bbmi471mvc3vibrb7xj1sr";
    };
  
    propagatedBuildInputs = [
  
negative.code:     mpdstats = enableMpd;
      mpdupdate = enableMpd;
      replaygain = enableReplaygain;
      thumbnails = enableThumbnails;
      web = enableWeb;
    };
  
    pluginsWithoutDeps = [
      "bench" "bpd" "bpm" "bucket" "convert" "cue" "duplicates" "embedart" "freedesktop"
      "fromfilename" "filefilter" "ftintitle" "fuzzy" "ihate" "importadded" "importfeeds"
      "info" "inline" "keyfinder" "lyrics" "mbcollection" "mbsync" "missing"
      "permissions" "play" "plexupdate" "random" "rewrite" "scrub" "smartplaylist"
      "spotify" "the" "types" "zero"
  