Clarify or conditionally skip GIS tests when optional GIS dependencies are missing

[Miraan08]

While setting up a clean development environment for contributing to mesa-examples, I ran the full test suite locally using:

python -m pytest

This resulted in a failure during collection of test_gis_examples.py due to missing optional GIS dependencies such as geopandas.

From reviewing the GitHub Actions workflow, it appears that CI runs test_examples.py but does not execute test_gis_examples.py, which suggests that GIS tests may be considered optional.

Would it make sense to either:

Document that GIS tests require additional optional dependencies, or

Conditionally skip GIS tests when dependencies such as geopandas are not available (for example, using pytest.importorskip)

This could help contributors working on non-GIS examples run the test suite without needing to install the full GIS stack.

Happy to explore a PR if this would be helpful.

[tejas243]

Hi, I would like to work on this issue. I can add conditional skipping of GIS tests using pytest.importorskip when geopandas is not installed. Please let me know if that approach is acceptable.