anchor.diff:  { lib, stdenv, fetchPypi, writeText, buildPythonPackage, isPy3k, pycairo
   , which, cycler, python-dateutil, numpy, pyparsing, sphinx, tornado, kiwisolver
   , freetype, qhull, libpng, pkg-config, mock, pytz, pygobject3, gobject-introspection
  -, certifi, pillow, fonttools, setuptools-scm, setuptools-scm-git-archive
  +, certifi, pillow, fonttools, setuptools-scm, setuptools-scm-git-archive, packaging
   , enableGhostscript ? true, ghostscript, gtk3
   , enableGtk3 ? false, cairo
   # darwin has its own "MacOSX" backend
  
positive.code: buildPythonPackage rec {
    version = "3.5.0";
    pname = "matplotlib";
  
    disabled = !isPy3k;
  
  
negative.code:     license     = with licenses; [ psfl bsd0 ];
      maintainers = with maintainers; [ lovek323 veprbl ];
    };
  }
  