Running in Errors module cv2 not found

[mixxor]

When i try to run your example i get this:

$ python3 -m cross2sheet.main http://web.mit.edu/puzzle/www/2014/puzzle/puzzle_with_answer_nowhere_man/grid.png nowhere_man.xlsx

Error: file format not recognized. If the grid is an HTML file, try taking a screenshot. If the grid is an image file, try converting it to PNG format.
The following warnings were encountered:
Image detection disabled because the module cv2 was not found.

[mixxor]

sorry for not digging into this to deep, i figured it out already:

this fixes the issue:

apt install python3-opencv