Build failes under ubuntu 13.04

Just tried to build current master under ubuntu raring, but I get an error (dependencies are installed with `sudo apt-get build-dep python-matplotlib` before) from the gtk check:

```

$ python setup.py build
============================================================================
Edit setup.cfg to change the build options

BUILDING MATPLOTLIB
            matplotlib: yes [1.3.x]
                python: yes [2.7.4 (default, Apr 19 2013, 18:28:01)  [GCC
                        4.7.3]]
              platform: yes [linux2]

REQUIRED DEPENDENCIES AND EXTENSIONS
                 numpy: yes [version 1.7.1]
              dateutil: yes [using dateutil version 1.5]
               tornado: yes [using tornado version 2.4.1]
             pyparsing: yes [using pyparsing version 1.5.7]
                 pycxx: yes [Couldn't import.  Using local copy.]
                libagg: yes [pkg-config information for 'libagg' could not
                        be found Using local copy.]
              freetype: yes [version 16.0.10]
                   png: yes [version 1.2.49]

OPTIONAL SUBPACKAGES
           sample_data: yes [installing]
              toolkits: yes [installing]
                 tests: yes [using nose version 1.1.2]

OPTIONAL BACKEND EXTENSIONS
                macosx: no  [Mac OS-X only]
                qt4agg: yes [Qt: 4.8.4, PyQt4: 4.10]
/usr/lib/python2.7/dist-packages/gi/overrides/Gtk.py:48: RuntimeWarning: You have imported the Gtk 2.0 module.
Because Gtk 2.0 was not designed for use with introspection some of the interfaces and API will fail.  As such this
is not supported by the pygobject development team and we encourage you to port your app to Gtk 3 or greater. 
PyGTK is the recomended python module to use with Gtk 2.0
  warnings.warn(warn_msg, RuntimeWarning)
Traceback (most recent call last):
  File "setup.py", line 131, in <module>
    result = package.check()
  File "/.../matplotlib/setupext.py", line 1451, in check
    success, msg = p.map(backend_gtk3agg_internal_check, [0])[0]
  File "/usr/lib/python2.7/multiprocessing/pool.py", line 250, in map
    return self.map_async(func, iterable, chunksize).get()
  File "/usr/lib/python2.7/multiprocessing/pool.py", line 554, in get
    raise self._value
AttributeError: 'gi.repository.Gtk' object has no attribute 'get_major_version'
```

It doesn't help to set `gtk = False` and `gtkagg = False` in `setup.cfg`