ci: isort: only target spond and tests dirs, as cannot get reliab…

…le behaviour which matches equivalent local command in root directory

.github/workflows/python-package.yml

@@ -32,12 +32,18 @@ jobs:
     - name: Install project
       run: poetry install
     - name: Lint imports with isort
-      # Use command line due to bugs/doc gaps with official `isort/isort-action`.
+      # Use command line due to bugs/docs gaps with official `isort/isort-action`.
       # Exit with error if the code is not properly formatted; show diffs;
-      # `black` compatibility
+      # `black` compatibility.
+      # Only target files in `spond` and `test` due to unreliable behaviour on files in
+      # root directory.
+      # Diffs reported for these files should be the same as fixes made by running
+      # `isort .` in the root project folder, which picks up config from
+      # `pyproject.toml`.
       run: |
         source $VENV
-        isort . --check-only --diff --profile black
+        isort spond --check-only --diff --profile black
+        isort tests --check-only --diff --profile black
     - name: Lint with black
       # by default: exit with error if the code is not properly formatted; show diffs
       uses: psf/black@stable