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