How to throw exception from JavaScript callback if it is executed through Selenium executeAsyncScript

I use Selenium WebDriver to automate some scripts. Most of the functionality is done using JavaScript endpoints, and I could not move this logic in Python:

// Python Selenium script 
data = self.driver.execute_async_script('selenium.get_data(arguments)')

// JavaScript placed somewhere on the page tested
selenium.get_data = function(args) {
    $.ajax({ 
        url:'http://servername/ajax_data', 
        success: function(data) {
            args[0](data);
        },
        error: function(data) {
            // here I would like to notify selenium that everything is broken
        }
    });
};

There is usually a certain point in JavaScript when I know that everything is already broken, and I would like to make an exception in the Selenium script. Of course, I could wait for a timeout, but the timeouts of my scripts are quite long, and I could not provide additional information about debugging in the error message.

(http://selenium.googlecode.com/svn/trunk/docs/api/java/org/openqa/selenium/JavascriptExecutor.html) (http://code.google.com/p/selenium/source/browse/trunk/java/client/test/org/openqa/selenium/ExecutingAsyncJavascriptTest.java?r=15810).

, :

        error: function(data) {
            window.alert(JSON.stringify(data));
        }

?