[v7r3] SingularityComputingElement: install python3 version

[fstagni]

BEGINRELEASENOTES

*Resources
CHANGE: SingularityComputingElement: install python3 version

ENDRELEASENOTES

[DIRACGridBot]

Sweep summary

Sweep ran in https://github.com/DIRACGrid/DIRAC/actions/runs/1667560338

Failed:

• integration
  cherry-pick d4efdf5 into integration failed
  check merge conflicts on a local copy of this repository

  git fetch upstream
  git checkout upstream/integration -b cherry-pick-2-d4efdf5d9-integration
  git cherry-pick -x -m 1 d4efdf5d9
  # Fix the conflicts
  git cherry-pick --continue
  git commit --amend -m 'sweep: #5716 SingularityComputingElement: install python3 version' --author='fstagni <[email protected]>'
  git push -u origin cherry-pick-2-d4efdf5d9-integration
  
  # If you have the GitHub CLI installed the PR can be made with
  gh pr create \
       --label 'sweep:from rel-v7r3' \
       --base integration \
       --repo DIRACGrid/DIRAC \
       --title '[sweep:integration] SingularityComputingElement: install python3 version' \
       --body 'Sweep #5716 `SingularityComputingElement: install python3 version` to `integration`.
  
  Adding original author @fstagni as watcher.
  
  BEGINRELEASENOTES
  
  *Resources
  CHANGE: SingularityComputingElement: install python3 version
  
  ENDRELEASENOTES
  Closes #1096287572'