shutil generate a NameError (WindowsError) exception when moving a
directory from an ext3 to a fat32 under linux

To reproduce it: 
under linux, current path on an ext3 filesytem, try to enter following
commands: 
mkdir toto #on an ext3 partition
python
import shutil
shutil.move("toto", "/media/fat32/toto") # /media/fat32 is mounted on a
fat32 filesystem

You will produce following error:
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.5/shutil.py", line 196, in move
    copytree(src, dst, symlinks=True)
  File "/usr/lib/python2.5/shutil.py", line 132, in copytree
    except WindowsError:
NameError: global name 'WindowsError' is not defined

Tested on ubuntu Feisty and a newly installed Hardy-beta.