[pepethecow]

I ran into this when trying to add a book to my library. The same error happens when I try to open an existing book in my library, but then the book does open.

calibre, version 5.21.0
ERROR: Errors while adding: Failed to add any books, click "Show details" for more information


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Failed to add the book: An Introduction to Machine Learning
D:/username/Desktop/Kubat2017_Book_AnIntroductionToMachineLearnin.epub
With error:
Traceback (most recent call last):
File "calibre\gui2\add.py", line 457, in add_book
File "calibre\db\legacy.py", line 334, in create_book_entry
File "calibre\db\cache.py", line 75, in call_func_with_lock
File "calibre\db\cache.py", line 1698, in create_book_entry
File "calibre\db\backend.py", line 920, in execute
apsw.CantOpenError: CantOpenError: unable to open database file

Any ideas? My database is not on a NAS, just a local disk.