Traceback (most recent call last):
  File "/usr/bin/calibre-parallel", line 20, in <module>
    sys.exit(main())
  File "/usr/lib/calibre/calibre/utils/ipc/worker.py", line 195, in main
    exec(sys.argv[-1])
  File "<string>", line 1, in <module>
  File "/usr/lib/calibre/calibre/srv/render_book.py", line 850, in viewer_main
    render_for_viewer(*args)
  File "/usr/lib/calibre/calibre/srv/render_book.py", line 841, in render_for_viewer
    return render(
  File "/usr/lib/calibre/calibre/srv/render_book.py", line 818, in render
    book_fmt, opfpath, input_fmt = extract_book(pathtoebook, output_dir, log=default_log)
  File "/usr/lib/calibre/calibre/ebooks/oeb/iterator/book.py", line 54, in extract_book
    plumber = Plumber(pathtoebook, tdir, log, view_kepub=view_kepub)
  File "/usr/lib/calibre/calibre/ebooks/conversion/plumber.py", line 755, in __init__
    raise ValueError('No plugin to handle input format: '+input_fmt)
ValueError: No plugin to handle input format: py