Drop support for Python 3.8?

[tomasr8]

Per https://devguide.python.org/versions/, Python 3.8 is now EOL.

Unless there is a specific reason to keep it around I think we should drop it.

From what I've seen when 3.7 was dropped, the deprecation could be announced in the next (2.17) release and removed in 2.18.

[akx]

We can consider it, but I'd rather still keep supporting it for a little longer.

According to https://pypistats.org/packages/babel some 6-10% of Babel downloads (all package versions, would need to look at the source BigTable data for a per-package-version breakdown) come from Python 3.8...

[tomasr8]

Wow that's higher than I would think! But yeah I agree, let's wait a bit