CI: Bypass pytest-xvfb and use xvfb-action instead

Author: effigies

.github/workflows/pythonpackage.yml

@@ -92,7 +92,9 @@ jobs:
     - name: Install test dependencies
       run: python -m pip install "niworkflows[tests]"
     - name: Run tests
-      run: pytest -sv --doctest-modules --cov niworkflows niworkflows
+      uses: GabrielBB/xvfb-action@v1
+      with:
+        run: pytest -sv --no-xvfb --doctest-modules --cov niworkflows niworkflows
 
   flake8:
     if: "!contains(github.event.head_commit.message, '[skip ci]')"