Use -P option to avoid that the source directory path gets automatica…

…lly added to sys.path while running pytest, since the multiphenicsx package should be loaded from the installation directory rather than the source one

.github/workflows/ci.yml

@@ -55,10 +55,10 @@ jobs:
           cd docs && make html
       - name: Run unit tests (serial)
         run: |
-          COVERAGE_FILE=.coverage_unit_serial python3 -m coverage run --source=multiphenicsx -m pytest tests/unit
+          COVERAGE_FILE=.coverage_unit_serial python3 -P -m coverage run --source=multiphenicsx -m pytest tests/unit
       - name: Run unit tests (parallel)
         run: |
-          COVERAGE_FILE=.coverage_unit_parallel mpirun -n 2 python3 -m coverage run --source=multiphenicsx --parallel-mode -m pytest tests/unit
+          COVERAGE_FILE=.coverage_unit_parallel mpirun -n 2 python3 -P -m coverage run --source=multiphenicsx --parallel-mode -m pytest tests/unit
       - name: Combine coverage reports
         run: |
           python3 -m coverage combine .coverage*
@@ -77,10 +77,10 @@ jobs:
           pattern: "tutorials/**/*.ipynb"
       - name: Run tutorials (serial)
         run: |
-          python3 -m pytest tutorials
+          python3 -P -m pytest tutorials
       - name: Run tutorials (parallel)
         run: |
-          python3 -m pytest --np 2 tutorials
+          python3 -P -m pytest --np 2 tutorials
       - name: Upload tutorials logs as an artifact in case of failure
         if: failure() || cancelled()
         uses: actions/upload-artifact@v3