Warn instead of error if there are invalid token lists

[BlinkyStitt]

Overview

I installed a list with invalid syntax. It installed without error, but the next time the process started, creating the manager erred with pydantic.error_wrappers.ValidationError: 63 validation errors for TokenList and a long list of the errors. It does not say what file it was processing.

Specification

If a file fails to load, instead of raising a ValidationError, a warning should be emitted with the name of the file.