You can use GUI with deDRM plugin to add an encrypted azw book with no problem.
You can also use calibredb.exe:
Code:
calibredb.exe add book.azw
the deDRM plugin will be called automatically, and it will successfully add the book.
However, it seems ebook-convert.exe doesn't support plugin, or at least not the deDRM one.
It will just error out at
mobi6.py L157 due to (obvious) `DRMError`.
According to
what kovidgoyal said before, I assume ebook-convert.exe is supposed to work exactly the same as conversion from the calibre GUI, so I think it's bug.
Thanks for your time!