File "/home/douglas/Desktop/flourish.gradebook/src/schooltool/gradebook/browser/stests/activity_categories.txt", line 10, in activity_categories.txt
Failed example:
    elements = browsers.manager.query_all.xpath('//form/input')
Exception raised:
    Traceback (most recent call last):
      File "/home/douglas/Desktop/flourish.gradebook/python/lib/python2.6/doctest.py", line 1253, in __run
        compileflags, 1) in test.globs
      File "<doctest activity_categories.txt[3]>", line 1, in <module>
        elements = browsers.manager.query_all.xpath('//form/input')
      File "/home/douglas/Desktop/flourish.gradebook/flourish/src/schooltool/testing/selenium.py", line 184, in find_element
        return self._wrap(method(param))
      File "/home/douglas/.buildout/eggs/selenium-2.6.0-py2.6.egg/selenium/webdriver/remote/webdriver.py", line 199, in find_elements_by_xpath
        return self.find_elements(by=By.XPATH, value=xpath)
      File "/home/douglas/.buildout/eggs/selenium-2.6.0-py2.6.egg/selenium/webdriver/remote/webdriver.py", line 533, in find_elements
        {'using': by, 'value': value})['value']
      File "/home/douglas/.buildout/eggs/selenium-2.6.0-py2.6.egg/selenium/webdriver/remote/webdriver.py", line 144, in execute
        self.error_handler.check_response(response)
      File "/home/douglas/.buildout/eggs/selenium-2.6.0-py2.6.egg/selenium/webdriver/remote/errorhandler.py", line 118, in check_response
        raise exception_class(message, screen, stacktrace)
    WebDriverException: Message: u'The given selector "//form/input is either invalid or does not resultin a Webelement. The following error occurred:\n[InvalidSelectorError] Unable to locate elements with the xpath expression //form/input because of the following error:\n[Exception... "Component returned failure code: 0x80070057 (NS_ERROR_ILLEGAL_VALUE) [nsIDOMXPathEvaluator.createNSResolver]"  nsresult: "0x80070057 (NS_ERROR_ILLEGAL_VALUE)"  location: "JS frame :: resource://fxdriver/modules/atoms.js :: <TOP_LEVEL> :: line 2360"  data: no]'