anchor.diff:  assert enableQt -> pyqt4 != null;
   
   buildPythonPackage rec {
  -  version = "2.1.2";
  +  version = "2.2.2";
     pname = "matplotlib";
     name = "${pname}-${version}";
   
     src = fetchurl {
       url = "mirror://pypi/m/matplotlib/${name}.tar.gz";
  -    sha256 = "725a3f12739d133adfa381e1b33bd70c6f64db453bfc536e148824816e568894";
  +    sha256 = "4dc7ef528aad21f22be85e95725234c5178c0f938e2228ca76640e5e84d8cde8";
     };
   
     NIX_CFLAGS_COMPILE = stdenv.lib.optionalString stdenv.isDarwin "-I${libcxx}/include/c++/v1";
  
positive.code: { stdenv, fetchurl, python, buildPythonPackage, pycairo, backports_functools_lru_cache
  , which, cycler, dateutil, nose, numpy, pyparsing, sphinx, tornado
  , freetype, libpng, pkgconfig, mock, pytz, pygobject3, functools32, subprocess32
  , enableGhostscript ? false, ghostscript ? null, gtk3
  , enableGtk2 ? false, pygtk ? null, gobjectIntrospection
  
negative.code:     ++ stdenv.lib.optional stdenv.isDarwin [ Cocoa ];
  
    propagatedBuildInputs =
      [ cycler dateutil nose numpy pyparsing tornado freetype kiwisolver
        libpng pkgconfig mock pytz ]
      ++ stdenv.lib.optional (pythonOlder "3.3") backports_functools_lru_cache
      ++ stdenv.lib.optional enableGtk2 pygtk
  