Streamline the environment matrix for Pip package tests

Keep:
- Ubuntu 24.04: with / without virtualenv
- Debian 13: with virtualenv
- MacOS 15 (ARM): with virtualenv
- Rocky Linux 10: with / without virtualenv
- Windows (2025): with / without virtualenv.

Author: popescu-v

.github/workflows/pip.yml

@@ -60,19 +60,14 @@ jobs:
       fail-fast: false
       matrix:
         env:
-          - {os: ubuntu-22.04, json-image: '{"image": "ubuntu:20.04"}'}
-          - {os: ubuntu-22.04, json-image: '{"image": null}'}
-          - {os: ubuntu-24.04, json-image: '{"image": null}'}
-          - {os: ubuntu-22.04, json-image: '{"image": "debian:trixie"}'}
-          - {os: ubuntu-22.04, json-image: '{"image": "rockylinux/rockylinux:8"}'}
-          - {os: ubuntu-22.04, json-image: '{"image": "rockylinux/rockylinux:9"}'}
-          - {os: ubuntu-22.04, json-image: '{"image": "rockylinux/rockylinux:10"}'}
-          - {os: windows-2022, json-image: '{"image": null}'}
-          - {os: windows-2025, json-image: '{"image": null}'}
-          - {os: macos-14, json-image: '{"image": null}'}
-          - {os: macos-15, json-image: '{"image": null}'}
-          - {os: macos-15-intel, json-image: '{"image": null}'}
-        use-virtualenv: [true, false]
+          - {os: ubuntu-24.04, json-image: '{"image": null}', use-virtualenv: true}
+          - {os: ubuntu-24.04, json-image: '{"image": null}', use-virtualenv: false}
+          - {os: ubuntu-22.04, json-image: '{"image": "debian:trixie"}', use-virtualenv: true}
+          - {os: ubuntu-22.04, json-image: '{"image": "rockylinux/rockylinux:10"}', use-virtualenv: true}
+          - {os: ubuntu-22.04, json-image: '{"image": "rockylinux/rockylinux:10"}', use-virtualenv: false}
+          - {os: windows-2025, json-image: '{"image": null}', use-virtualenv: true}
+          - {os: windows-2025, json-image: '{"image": null}', use-virtualenv: false}
+          - {os: macos-15, json-image: '{"image": null}', use-virtualenv: true}
     runs-on: ${{ matrix.env.os }}
     container: ${{ fromJSON(matrix.env.json-image) }}
     steps:
@@ -101,12 +96,6 @@ jobs:
             VENV_ACTIVATE="khiops-venv/bin/activate"
           fi
           echo "VENV_ACTIVATE=$VENV_ACTIVATE" >> "$GITHUB_ENV"
-          # Centralise the venv condition
-          if [[ "${{ fromJSON(matrix.env.json-image).image }}" == "debian:trixie" || "${{ matrix.use-virtualenv }}" == "true" ]]; then
-            echo "USE_VENV=true" >> "$GITHUB_ENV"
-          else
-            echo "USE_VENV=false" >> "$GITHUB_ENV"
-          fi
           # Setup Python (be portable wrt. python vs python3 in runners and
           # containers; either python3 or python is present as per the Python
           # installation step in the Docker container contexts)
@@ -140,8 +129,8 @@ jobs:
 
           # Install the Khiops Python library
 
-          # Use a virtualenv if running on Debian 13 (mandatory) or if required
-          if [[ "$USE_VENV" == "true" ]]; then
+          # Use a virtualenv if required
+          if [[ "${{ matrix.env.use-virtualenv }}" == "true" ]]; then
             $PYTHON -m venv khiops-venv
             source "$VENV_ACTIVATE"
           fi
@@ -162,7 +151,7 @@ jobs:
           rm -f requires-khiops.txt requires-no-khiops.txt
           # Lastly, install khiops-python
           $PYTHON -m pip install khiops*.tar.gz
-          if [[ "$USE_VENV" == "true" ]]; then
+          if [[ "${{ matrix.env.use-virtualenv }}" == "true" ]]; then
             deactivate
           fi
       - name: Run tests
@@ -182,8 +171,8 @@ jobs:
           # modules are currently not initializing the shell anyway
           if [ -n "$MODULESHOME" ]; then module unload mpi; fi
 
-          # Use a virtualenv if running on Debian 13 (mandatory) or if required
-          if [[ "$USE_VENV" == "true" ]]; then
+          # Use a virtualenv if required
+          if [[ "${{ matrix.env.use-virtualenv }}" == "true" ]]; then
             source "$VENV_ACTIVATE"
           fi
           if [[ -n "${{ fromJSON(matrix.env.json-image).image }}" ]]; then
@@ -206,7 +195,7 @@ jobs:
           # The MPI command is not always named mpiexec, but can be orterun etc
           # (as given by khiops_env)
           kh-status | grep "MPI command" | grep -vwq "<empty>"
-          if [[ "$USE_VENV" == "true" ]]; then
+          if [[ "${{ matrix.env.use-virtualenv }}" == "true" ]]; then
             deactivate
           fi
       - name: Test package / Git tag version coherence
@@ -215,14 +204,14 @@ jobs:
         run: |
           # Don't exit on first error: print relevant error message
           set +e
-          # Use a virtualenv if running on Debian 13 (mandatory) or if required
-          if [[ "$USE_VENV" == "true" ]]; then
+          # Use a virtualenv if required
+          if [[ "${{ matrix.env.use-virtualenv }}" == "true" ]]; then
             source "$VENV_ACTIVATE"
           fi
           # Convert pre-release version specification in the Git tag to the Pip
           # format and check that it matches the Pip package version
           PACKAGE_VERSION=$($PYTHON -m pip show khiops | awk 'BEGIN {FS = ": "} $1 ~ /^Version$/ {print $2}')
-          if [[ "$USE_VENV" == "true" ]]; then
+          if [[ "${{ matrix.env.use-virtualenv }}" == "true" ]]; then
             deactivate
           fi
           echo "${{ github.ref_name }}" | tr -d '-' | rev | sed -E 's/\.([^0-9].*)/\1/' | rev | \