demandimport: blacklist sqlalchemy.events as it has side effects (issue5085) Importing sqlalchemy.events cannot be delayed as it registers classes to their event mechanism. It worked fine before 4f1144c3c72b, since they use new-style imports. But now we have to blacklist it because our demandimport can handle new-style imports. This patch series isn't intended for stable as we don't guarantee API compatibility with 3rd-party extensions. They can temporarily disable the demand importer to work around the issue.