In 2015, there was no way I could have moved to Python 3. There were too many libraries I depended on that hadn't ported yet. In 2019, I feel pretty confident about using Python 3, having used it exclusively for about 18 months now. For my personal use case at least, this timeline worked out well for me. Hopefully it works out for most everyone. I can't imagine they made this decision without at least some data backi…
Based on your timeline, a four year gap from "not yet ready to migrate" to "we won't fix security vulnerabilities" is very short. Python is an open source project I've used and contributed nothing to, so I don't have the right to be a back seat driver. Were it a commercial project and I was a customer, I would be quite upset.
I feel like this the python community has been the epitome of class regarding communication during a transition.