Why do I get this field is required error when uploading files (Flask, WTForms)?

Question

Flask

Actually, the point is in the title. I'm trying to make a form for creating/editing a post with two images. When I try to submit the form, the validation for both FileFields fails with the wording "This field is required", although I selected the files. What am I doing wrong? Enctype for the form specified. Everything is started on the local server.

Code on pastebin

Answer 1

Apparently the FileRequired validator does not support python3 well, since I did not observe such a problem in 2.7. I wrote my custom validator, as soon as I have free time I will try to deal with the problem and fix the native one.