Inform user that an opened file under Windows can't be synchronized

2015-01-22 12:05:21,229 4692 4864 WARNING  nxdrive.synchronizer Delaying local update of remotely modified content LastKnownState<local_folder=u'Nuxeo Drive', local_path=u'/path/file.xlsx', remote_name=u'file.xlsx', local_state=u'synchronized', remote_state=u'modified', pair_state=u'remotely_modified', error_count=2> due to concurrent file access (probably opened by another process).
2015-01-22 12:05:21,230 4692 4864 ERROR    nxdrive.synchronizer Failed to sync LastKnownState<local_folder=u'Nuxeo Drive', local_path=u'/path/file.xlsx', remote_name=u'file.xlsx', local_state=u'synchronized', remote_state=u'modified', pair_state=u'remotely_modified', error_count=2>, blacklisting doc pair for 300 seconds
Traceback (most recent call last):
  File "nuxeo-drive-client\nxdrive\synchronizer.py", line 1513, in synchronize
  File "nuxeo-drive-client\nxdrive\synchronizer.py", line 799, in synchronize_one
  File "nuxeo-drive-client\nxdrive\synchronizer.py", line 929, in _synchronize_remotely_modified
WindowsError: [Error 32] Le processus ne peut pas acc\E9der au fichier car ce fichier est utilis\E9 par un autre processus: u'\\\\?\\C:\\Users\\bran9576\\Documents\\Nuxeo Drive\\path\\file.xlsx'