Drag'n'drop image in windows not working

[David Lefever @ Taktik]

When adding a binary field with an image widget, a user is able to drag and drop an image to the field.
This works with Linux and Mac, but not in Windows under certain circumstances.

I could reproduce the bug when I try to drop an image from a folder containing an accent, for instance:
C:\été\Collines.jpg

The stacktrace:
Traceback (most recent call last):
  File "widget\view\form_gtk\image.pyo", line 163, in drag_data_received
  File "urllib.pyo", line 86, in urlopen
  File "urllib.pyo", line 205, in open
  File "urllib.pyo", line 467, in open_file
  File "urllib.pyo", line 481, in open_local_file
IOError: [Errno 2] Le chemin d'accès spécifié est introuvable: 'C:\\\xc3\xa9t\xc3\xa9\\Collines.jpg'

Thank you,
David