> > It was decided to start deprecating the asyncore, asynchat and smtpd
> > modules in Python 3.6 released in 2016, 5 years ago. Python 3.10 emits
> > DeprecationWarning.
>
> Wait, only Python 3.10?
> According to the policy, the warning should be there for *at least* two
> releases. (That's a minimum, for removing entire modules it might make
> sense to give people even more time.)

The PEP 387 says "Similarly a feature cannot be removed without notice
between any two consecutive releases."

It is the case here. The 3 modules are marked as deprecated for 4
releases in the documentation: Python 3.6, 3.7, 3.9 and 3.10. Example:
https://docs.python.org/3.6/library/asyncore.html