Part of the issue is that you can't just generalize it to "breaking changes." Ruby, very similar to Python, underwent a similar break between Ruby 1.8 and Ruby

Part of the issue is that you can't just generalize it to "breaking changes." Ruby, very similar to Python, underwent a similar break between Ruby 1.8 and Ruby 1.9, but didn't befall the same fate. The specifics really matter in this kind of analysis.