Bumped Python to 3.8.12

I have downloaded the source tarball to compute the SHA256 sum.
I did check its GPG signature (same key as 3.8.10, that I previously
also checked)

--HG--
branch : heptapod
5 jobs for !46 with topic/heptapod/py-3.8.12 in 78 minutes and 26 seconds (queued for 6 seconds)
latest detached
Status Name Job ID Coverage
  Test
passed rspec #246881

00:00:59

 
  Package
passed pkg-ubuntu-focal #246985

01:13:59

failed pkg-ubuntu-focal #246882

00:15:24

 
  Docker
passed docker-testing #246883

00:03:28

 
  Functional
skipped heptapod-tests-default