anchor.diff:  { lib, stdenv
   , buildPythonPackage
   , fetchPypi
  +, unzip
  +, pythonOlder
   , libGL
   , libGLU
   , xorg
  -, future
  -, pytest
  +, pytestCheckHook
   , glibc
   , gtk2-x11
   , gdk-pixbuf
   , fontconfig
   , freetype
   , ffmpeg-full
  +, openal
  +, libpulseaudio
   }:
   
   buildPythonPackage rec {
  -  version = "1.4.2";
  +  version = "1.5.19";
     pname = "pyglet";
  +  disabled = pythonOlder "3.6";
   
     src = fetchPypi {
       inherit pname version;
  -    sha256 = "1dxxrl4nc7xh3aai1clgzvk48bvd35r7ksirsddz0mwhx7jmm8px";
  +    sha256 = "sha256-/kuh2RboWWoOs4KX0PyhNlYgKI8q2SyiWvMJvprg/8w=";
  +    extension = "zip";
     };
   
     # find_library doesn't reliably work with nix (https://github.com/NixOS/nixpkgs/issues/7307).
  
positive.code:                 path = '${freetype}/lib/libfreetype${ext}'
              elif name[0:2] == 'av' or name[0:2] == 'sw':
                  path = '${ffmpeg-full}/lib/lib' + name + '${ext}'
              if path is not None:
                  return ctypes.cdll.LoadLibrary(path)
          raise Exception("Could not load library {}".format(names))
      EOF
    '';
  
    propagatedBuildInputs = [ future ];
  
    # needs an X server. Keep an eye on
    # https://bitbucket.org/pyglet/pyglet/issues/219/egl-support-headless-rendering
    doCheck = false;
  
    checkInputs = [
      pytest
    ];
  
    checkPhase = ''
      py.test tests/unit tests/integration
    '';
  
    meta = with lib; {
      homepage = "http://www.pyglet.org/";
  
negative.code:             path = None
              if name == 'GL':
                  path = '${libGL}/lib/libGL${ext}'
              elif name == 'EGL':
                  path = '${libGL}/lib/libEGL${ext}'
              elif name == 'GLU':
                  path = '${libGLU}/lib/libGLU${ext}'
              elif name == 'c':
  