add try on test sdist

Author: blink1073

.github/workflows/python-tests.yml

@@ -137,6 +137,8 @@ jobs:
     steps:
       - uses: jupyterlab/maintainer-tools/.github/actions/base-setup@v1
       - uses: jupyterlab/maintainer-tools/.github/actions/test-sdist@v1
+        with:
+          test_command: pytest --vv || pytest -vv --lf
 
   python_tests_check: # This job does nothing and is only used for the branch protection
     if: always()