That said, I remember all three of those transitions (2.3 to 2.4, 2.4 to 2.5, and 2.5 to 2.6), and I remember changing Python code to make use of new features introduced in those transitions (for example, using with statements and context managers in 2.5), but those aren't breaking changes; the old code still worked, it just wasn't as robust as using the new features.
