[stdlib-sig] standardizing the deprecation policy (and how noisy they are)

[Antoine Pitrou]

> One is to keep things as is, but to require two releases with
> PendingDeprecationWarning so there are three years of
> silent-by-default warnings to update your code. But that last release
> before removal came would still be noisy.

While deprecation warnings are noisy, I also think it's the best
compromise we can think of.
Making them silent by default would be worse, except for those very few
programs/libraries which have absolutely 100% test coverage.

Regards

Antoine.