[BeckyEbook]

@KevinH: So maybe to avoid the problem after conversion, give a warning about it? It's not about laziness either, but a reminder that there is still "something" to be done before starting the plugin so that everything goes according to plan.

Something like that:

Spoiler:

    file_list = list(bk.text_iter())
    for (html_id, href) in file_list:
        filename = os.path.basename(href)
        if bk.launcher_version() >= 20190927:
            filename = bk.id_to_bookpath(html_id)

        if not '.xhtml' in filename:
            print("Error: ePub3-itizer requires .xhtml extension for html files")
            print("Change the extension for all html files to .xhtml and run the plugin again")
            return -1