anchor.diff:    });
   
     fs = buildPythonPackage rec {
  -    name = "fs-0.4.0";
  -
  -    src = fetchurl {
  -      url    = "https://pyfilesystem.googlecode.com/files/fs-0.4.0.tar.gz";
  -      sha256 = "1fk7ilwd01qgj4anw9k1vjp0amxswzzxbp6bk4nncp7210cxp3vz";
  +    name = "fs-0.5.0";
  +
  +    src = fetchurl {
  +      url    = "https://pypi.python.org/packages/source/f/fs/${name}.tar.gz";
  +      sha256 = "144f4yn2nvnxh2vrnmiabpwx3s637np0d1j1w95zym790d66shir";
       };
   
       meta = with stdenv.lib; {
  
positive.code:       url = "http://pypi.python.org/packages/source/m/musicbrainzngs/${name}.tar.gz";
        md5 = "9e17a181af72d04a291c9a960bc73d44";
      };
  
      meta = {
        homepage = http://alastair/python-musicbrainz-ngs;
  
negative.code: 
  
    munkres = buildPythonPackage rec {
      name = "munkres-1.0.6";
  
      src = fetchurl {
        url = "http://pypi.python.org/packages/source/m/munkres/${name}.tar.gz";
        md5 = "d7ba3b8c5001578ae229a2d5a655872f";
      };
  
      # error: invalid command 'test'
  