[$] Python and deprecations redux

The problem of how to deprecate pieces of the Python languagein a minimally disruptive way has cropped in various guises over the last few years-in truth,it has been wrangled with throughout much of language's 30-year history.The scars of the biggest deprecation, that of Python 2, are still ratherfresh, both for users and the core developers, so no one wants (or plans)a monumental change of that sort. But the language community does want tocontinue evolving Python, which means leaving some "baggage" behind; howto do so without leaving further scars is a delicate balancing act, as yetanother discussion highlights.