Fixate the python container version

[afroch]

Summary

This pull request introduces the following changes

• This fixes the python container version to 3.8.15. The fix introduced by Fixing dubious owner issue in pages pipeline #152 is not working for main. Unfortunately, there was a bigger update to git and the pipelines are not running correctly with the new version. This fixes that for now

Conformity

• Changelog entry
• Documentation

[codecov-commenter]

Codecov Report

Merging #153 (537a47f) into main (35bab42) will not change coverage.
The diff coverage is n/a.

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@@           Coverage Diff           @@
##             main     #153   +/-   ##
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  Coverage   96.50%   96.50%           
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  Files          30       30           
  Lines        2663     2663           
=======================================
  Hits         2570     2570           
  Misses         93       93           

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[samvanstroud]

Is it worth bumping the minimum python version? to e.g. 3.10?