[WIP] Include Python 3.8 images

[fubarhouse]

Checklist

• Affected Issues have been mentioned in the Closing issues section
• Documentation has been written/updated
• PR title is ready for changelog and subsystem label(s) applied

Changelog Entry

Add images for use of Python 3.8

Closing issues

TBC

[tobybellwood]

Ugh - this has just gave me a flashback - as soon as Alpine shifted their Python3 package from 3.7 to 3.8, we've inadvertently also installed 3.8 alongside in our 3.7 images...

(because we use python dockerhub images, but then have to use apk to add python3-dev packages
https://github.com/amazeeio/lagoon/blob/master/images/python/Dockerfile#L37-L38)

We'll have to rethink our use of apk here (I foreshadowed this in #1531 (comment))

Or only support a single version of Python3

python:/$ apk info | grep python3
python3
python3-dev
python:/$ which python
/usr/local/bin/python
python:/$ find / -name python
/usr/local/bin/python
python:/$ /usr/local/bin/python -V
Python 3.7.7
python:/$ find / -name python3
/usr/bin/python3
/usr/local/bin/python3
python:/$ /usr/local/bin/python3 -V
Python 3.7.7
python:/$ /usr/bin/python3 -V
Python 3.8.2

[fubarhouse]

In regards to #1531 (comment), my vote would go to supporting one version via the system package manager...

Package management is tricky but if you are managing system packages along-side language specific package managers, maintenance is a lot better when using the system package manager....