Debub failing xarray import in unstable CI

.github/workflows/ci.yaml

@@ -73,6 +73,7 @@ jobs:
       - name: Run unit tests
         shell: bash -l {0}
         run: |
+          python -c "from xarray.backends.api import open_dataset"
           pytest --cov=trollimage trollimage/tests --cov-report=xml --cov-report=
 
       - name: Upload unittest coverage to Codecov