PySide6 python-package workflow: offscreen

Author: PierreRaybaut

.github/workflows/python-package-PySide6.yml

@@ -46,4 +46,5 @@ jobs:
         flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
     - name: Test with pytest
       run: |
+        echo "QT_QPA_PLATFORM=offscreen" >> "$GITHUB_ENV"
         pytest