Traceback (most recent call last):
  File "/usr/bin/fix_noto_cjk_thin.py", line 88, in <module>
    main(sys.argv)
  File "/usr/bin/fix_noto_cjk_thin.py", line 84, in main
    fix_font(font_filename)
  File "/usr/bin/fix_noto_cjk_thin.py", line 32, in fix_font
    assert source_filename.endswith(".otf")
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError