'Completion still happens even if a command-line is given
that would normally throw UsageError.
The existence of --unknown-option prior to the subcommand
will break subcommand detection... but we complete anyway'

def test_incompleteCommandLine_case2(self):

    outputFile = BytesIO()
    self.patch(usage.Options, '_shellCompFile', outputFile)
    opts = FighterAceOptions()
    self.assertRaises(SystemExit, opts.parseOptions, ['--fokker', '--unknown-option', 'server', '--list-server', '--_shell-completion', 'zsh:5'])
    outputFile.seek(0)
    self.assertEqual(1, len(outputFile.read(1)))
    outputFile.seek(0)
    outputFile.truncate()
