[8.0] Use apptainer for SingularityComputingElement and enhance debugging

[chrisburr]

BEGINRELEASENOTES

*WorkloadManagement
CHANGE: Use apptainer for SingularityComputingElement
CHANGE: Drop support for SingularityComputingElement without user namespaces
CHANGE: Enchance debugging output if SingularityComputingElement fails
CHANGE: Drop support for using apptainer from outside of DIRACOS2

ENDRELEASENOTES

[aldbr]

Shouldn't we use apptainer instead of singularity here?

DIRAC/src/DIRAC/Resources/Computing/SingularityComputingElement.py

Line 68 in b16c65b

FALLBACK_SINGULARITY = "/cvmfs/oasis.opensciencegrid.org/mis/singularity/current/bin"

$ ls -l /cvmfs/oasis.opensciencegrid.org/mis/
total 228
drwxrwxr-x. 33 cvmfs cvmfs   4096 Dec 16 21:48 apptainer
drwxr-xr-x. 29 cvmfs cvmfs   4096 Apr  3  2024 singularity

[chrisburr]

FALLBACK_SINGULARITY was now unused so I've removed it.

[DIRACGridBot]

Sweep summary

Sweep ran in https://github.com/DIRACGrid/DIRAC/actions/runs/12985893600

Failed:

• integration
  cherry-pick 78d20af into integration failed
  check merge conflicts on a local copy of this repository

  git fetch upstream
  git checkout upstream/integration -b cherry-pick-2-78d20afae-integration
  git cherry-pick -x -m 1 78d20afae
  # Fix the conflicts
  git cherry-pick --continue
  git commit --amend -m 'sweep: #8000 Use apptainer for SingularityComputingElement and enhance debugging' --author='Chris Burr <[email protected]>'
  git push -u origin cherry-pick-2-78d20afae-integration
  
  # If you have the GitHub CLI installed the PR can be made with
  gh pr create \
       --label 'sweep:from rel-v8r0' \
       --base integration \
       --repo DIRACGrid/DIRAC \
       --title '[sweep:integration] Use apptainer for SingularityComputingElement and enhance debugging' \
       --body 'Sweep #8000 `Use apptainer for SingularityComputingElement and enhance debugging` to `integration`.
  
  Adding original author @chrisburr as watcher.
  
  BEGINRELEASENOTES
  
  *WorkloadManagement
  CHANGE: Use apptainer for SingularityComputingElement
  CHANGE: Drop support for SingularityComputingElement without user namespaces
  CHANGE: Enchance debugging output if SingularityComputingElement fails
  CHANGE: Drop support for using apptainer from outside of DIRACOS2
  
  ENDRELEASENOTES
  Closes #8009'