Consider running python tests for releases, and PRs (if they modify anything in the data directory)

[Greenheart]

Do we actually run Python tests during for releases and PRs? Both our GitHub workflows have the python tests commented out:

klimatkollen/.github/workflows/pr_check.yml

Lines 61 to 64 in b10f498

	# Run Python tests
	# Fixme: Uncomment when tests are added!
	# - name: Run Python tests
	# run: python3 -m unittest discover -s data/tests

and

klimatkollen/.github/workflows/release.yml

Lines 61 to 64 in b10f498

	# Run Python tests
	# Fixme: Uncomment when tests are added!
	# - name: Run Python tests
	# run: python3 -m unittest discover -s data/tests

To make the Python tests only run when something has changed in the data directory (where the Python code exists), we might be use a command similar to this in the build step:

git diff --quiet HEAD^ HEAD data

This is commonly used to conditionally perform Vercel builds for projects where you only want specific changes to trigger new builds.