Question: Where to define the Exceptions [Appendix E: Validation] #89

Hello, I am currently reading the Appendix Validation. As I can't find a branch for that I'm going to ask my question here:

Where to define the ValidationError?
The validation error is used in the flask_app.py, redis_pubsub.py and potentially many more positions on different layers [page 260].
Should I create a general exceptions.py file in the src directory for broad exceptions like this?