See https://discuss.tryton.org/t/should-run-tests-report-something-on-import-error-of-modules/2748
When using run-tests ImportErrors are caught in tryton_test.py modules_suite. These errors are relevant for development and help correct mistakes when writing tests.
It seems that this exception is not raised for historical reasons and we could just let it be raised now.
Added an issue and submitted a patch Let exception ImportError be raised (run-tests) (#9359) · Issues · Tryton / Tryton · GitLab