CI: Use xdist to speed up tests

Author: effigies

.github/workflows/pythonpackage.yml

@@ -184,7 +184,7 @@ jobs:
     - name: Install test dependencies
       run: python -m pip install "niworkflows[tests]"
     - name: Run tests
-      run: pytest -sv --doctest-modules --cov niworkflows niworkflows
+      run: pytest -sv --doctest-modules -n auto --cov niworkflows niworkflows
     - uses: codecov/codecov-action@v3
       name: Submit to CodeCov
 
@@ -244,7 +244,7 @@ jobs:
     - name: Install test dependencies
       run: python -m pip install $PIP_FLAGS "niworkflows[tests]"
     - name: Run tests
-      run: pytest -sv --doctest-modules --cov niworkflows niworkflows
+      run: pytest -sv --doctest-modules -n auto --cov niworkflows niworkflows
     - uses: codecov/codecov-action@v3
       name: Submit to CodeCov