Failing test `test_create_ebook`

[og-abdul-mateen]

Hi, when I run the tests, I get the following result.

FAILED tests/test_create_ebook.py::test_create_ebook - AssertionError: [Message(id='MED_013', level='ERROR', location='on_the_duty_of_civil_disobedience.epub/epub/content.opf:46:100', messa...le parsing file: media overlay items must be of...

======================================================================== 1 failed, 4 passed, 176 warnings in 17.60s =========================================================================

Also, the generated synced files don't work in any Ebook reader. Audio and text work separately, but not with Media Overlays.