python3: Update to 3.9.7

[mkoeppe]

released 2021-08-30, with numerous fixes - https://docs.python.org/3/whatsnew/changelog.html

previous update: 3.9.6 in #32104

CC: @dimpase

Component: packages: standard

Author: Matthias Koeppe

Branch/Commit: e0c968e

Reviewer: Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/32443

[mkoeppe]

Branch: u/mkoeppe/python3__update_to_3_9_7

[mkoeppe]

Reviewer: https://github.com/mkoeppe/sage/actions/runs/1210670742

[mkoeppe]

Author: Matthias Koeppe

[mkoeppe]

Commit: e0c968e

[mkoeppe]

New commits:

e0c968e

build/pkgs/python3: Update to 3.9.7

[mkoeppe]

Changed reviewer from https://github.com/mkoeppe/sage/actions/runs/1210670742 to https://github.com/mkoeppe/sage/actions/runs/1210670742, ...

[mkoeppe]

comment:3

Tests look clean, ready for review

[dimpase]

comment:4

lgtm

[dimpase]

Changed reviewer from https://github.com/mkoeppe/sage/actions/runs/1210670742, ... to Dima Pasechnik

[vbraun]

Changed branch from u/mkoeppe/python3__update_to_3_9_7 to e0c968e