But hey, if some 3rd party group effectively forks the language and maintains a Python2 branch after the official EOL date, good on them. But I'd argue that using that is risky in the same way that using a Pale Moon or Waterfox is (arguably) riskier than using mainstream Firefox.
For what it’s worth, Perl 6 can load Perl 5 libraries: https://github.com/niner/Inline-Perl5
Python3 broke compatibility for spurious reasons. The language didn't change that much, it could have kept compatibility with minor concessions.
> Java or COBOL maybe have done a better job of not breaking backwards compatibility...
Literally every single other major language has done a better job at it. That's a big part of why they are major languages. Also, most of these are statically typed, so any minor breaking change is far less risky to pull off.
> ...but Python 3 isn't exactly Perl 6 here.
Well, maybe if Perl6 didn't happen Perl wouldn't be irrelevant today.
C++'s upgrade woes make Python 3 look downright trivial in comparison.
If you're talking about ABI breaking, that's a different story. Python breaks the ABI in every major release as well. That generally requires a recompile, not a major code migration.
Python2 will almost certainly still remain in widespread use and it will still get security updates through alternative distribution channels. It's not that much work fixing such relatively rare issues versus migrating a major codebase.