Check expected error messages in BEP3 test suite

[denalimarsh]

yeah, that's why I changed it to require. Otherwise, it reuses the state. We can do a test cleanup in another PR since it's out of scope from this one

_Originally posted by @fedekunze in https://github.com/render_node/MDI0OlB1bGxSZXF1ZXN0UmV2aWV3Q29tbWVudDQyMjY5MzA3MA==/comments/review_comment