'The checker created by the C{--auth} command-line option returns a
L{Deferred} that fails with L{UnauthorizedLogin} when
presented with credentials that are unknown to that checker.'

def test_authFailure(self):

    self.options.parseOptions(['--auth', ('file:' + self.filename)])
    checker = self.options['credCheckers'][(-1)]
    invalid = credentials.UsernamePassword(self.usernamePassword[0], 'fake')
    return checker.requestAvatarId(invalid).addCallbacks((lambda ignore: self.fail('Wrong    password    should    raise    error')), (lambda err: err.trap(error.UnauthorizedLogin)))
