RemoteMountFailedError 'Max. number of password inputs reached' not handled properly

The issue was originally reported by Jim Caughran on 2010-11-29 (here: https://bugs.launchpad.net/ubuntu/+source/sbackup/+bug/671785):

entering SMB address, password had * but no /

Sorry, this should not have happened
An uncaught error occurred. Close this message window and restart the application.
Please report this error on https://bugs.launchpad.net/sbackup.
Max. number of password inputs reached. Aborted.

Traceback (most recent call last):
  File "/usr/share/sbackup/sbackup/fs_backend/_gio_utils.py", line 232, in _ask_password_cb
    raise exceptions.RemoteMountFailedError("Max. number of password inputs reached. Aborted.")
RemoteMountFailedError: Max. number of password inputs reached. Aborted.

Error related to user input (passwords) should be handled in a more graceful manner.