Thanks for your responses to my comments. I'm working as hard as I can to get my customer's systems migrated into the Python 3 world, and I appreciate the efforts of the community to provide incentives (such as the resolution for this failure) for developers to upgrade. However, it's a delicate balancing act sometimes, given that we have critical places in our system for which the same code runs more than twice as slowly on Python 3.6 as on Python 2.7.