'Test that the usage mixin exits when trying to use a non existent
reactor (the name not matching to any reactor), giving an error
message.'

def test_reactorSelectionMixinNonExistent(self):

    class ReactorSelectionOptions(usage.Options, app.ReactorSelectionMixin, ):
        pass
    self.pluginResults = []
    options = ReactorSelectionOptions()
    options.messageOutput = NativeStringIO()
    e = self.assertRaises(usage.UsageError, options.parseOptions, ['--reactor', 'fakereactortest', 'subcommand'])
    self.assertIn('fakereactortest', e.args[0])
    self.assertIn('help-reactors', e.args[0])
