wordpress: functional test to create post fails in testing

_______________________________________________ test_post ________________________________________________

self = <splinter.element_list.ElementList object at 0x7fe9d2c96a30>, index = 0

    def __getitem__(self, index):
        if not isinstance(index, int) and not isinstance(index, slice):
            return self.first[index]
        try:
>           return self._container[index]
E           IndexError: list index out of range

../../../.local/lib/python3.9/site-packages/splinter/element_list.py:42: IndexError

During handling of the above exception, another exception occurred:

session_browser = <splinter.driver.webdriver.firefox.WebDriver object at 0x7fe9d2d2a400>

    def test_post(session_browser):
        """Test writing a blog post."""
        functional.app_enable(session_browser, 'wordpress')
>       _write_post(session_browser, 'FunctionalTest')

plinth/modules/wordpress/tests/test_functional.py:36: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
plinth/modules/wordpress/tests/test_functional.py:134: in _write_post
    browser.find_by_id('post-title-0').fill(title)
../../../.local/lib/python3.9/site-packages/splinter/element_list.py:76: in __getattr__
    return getattr(self.first, name)
../../../.local/lib/python3.9/site-packages/splinter/element_list.py:57: in first
    return self[0]
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <splinter.element_list.ElementList object at 0x7fe9d2c96a30>, index = 0

    def __getitem__(self, index):
        if not isinstance(index, int) and not isinstance(index, slice):
            return self.first[index]
        try:
            return self._container[index]
        except IndexError:
>           raise ElementDoesNotExist(
                u'no elements could be found with {0} "{1}"'.format(
                    self.find_by, self.query
                )
            )
E           splinter.exceptions.ElementDoesNotExist: no elements could be found with id "post-title-0"

../../../.local/lib/python3.9/site-packages/splinter/element_list.py:44: ElementDoesNotExist