[Python-Dev] Re: Request to postpone some Python 3.9 incompatible changes to Python 3.10

Is it possible to change some of those deprecation from Warn-by-default (but can add a warning filter to make them error) to error-by-default (but can add a filter to make them only warnings). That way it is easy to fix large projects (even w/o modifying the source) in only a couple of lines of codes; and they buy themselves a year or so and remove in 3.10. That way you have a more gradual transition; and a clear signal to project with a last chance to fix issues. And that way can't complained they did not know as they have to opt-in.