Does the gtk3agg backend work on python3?

Whatsnew indicates that the gtk3agg backend works on python3. However 
backend_gtk3agg.py still contains a warning about in not working:

```python
warnings.warn("The Gtk3Agg backend is not known to work on Python 3.x.")
```

and I'm still seeing the error given in the original pull request (#590) when using this backend on python3
on ubuntu 12.04. 
```python
NotImplementedError: Surface.create_for_data: Not Implemented yet.
```

Does it work with more resent versions of the gtk3 bindings for python3?

Edit: Ubuntu 12.04 ships with python3-gi 3.2.2