[codedr]

I tried to open a book in my library. I got 'Failed to open the book...' with the following trace back.

I was able to successfully open the book with okular.
I believe I opened this book before with an older version of calibre.

Traceback (most recent call last):
  File "/usr/bin/calibre-parallel", line 20, in <module>
    sys.exit(main())
  File "/usr/lib64/calibre/calibre/utils/ipc/worker.py", line 188, in main
    exec(sys.argv[-1])
  File "<string>", line 1, in <module>
  File "/usr/lib64/calibre/calibre/srv/render_book.py", line 829, in viewer_main
    render_for_viewer(*args)
  File "/usr/lib64/calibre/calibre/srv/render_book.py", line 822, in render_for_viewer
    extract_annotations=True, virtualize_resources=False, max_workers=0
  File "/usr/lib64/calibre/calibre/srv/render_book.py", line 801, in render
    book_metadata=mi, virtualize_resources=virtualize_resources
  File "/usr/lib64/calibre/calibre/srv/render_book.py", line 602, in process_exploded_book
    raster_cover_name, titlepage_name = create_cover_page(container, input_fmt.lower(), is_comic, book_metadata)
  File "/usr/lib64/calibre/calibre/srv/render_book.py", line 304, in create_cover_page
    titlepage_name, raster_cover_name = find_epub_cover(container)
  File "/usr/lib64/calibre/calibre/srv/render_book.py", line 255, in find_epub_cover
    first_page_name = next(container.spine_names)[0]