set PYTHONPATH properly

Author: parmentelat

.github/workflows/myst-to-pages.yml

@@ -60,10 +60,13 @@ jobs:
         run: |
           source venv/bin/activate
           npm install mystmd
+      - name: Set PYTHONPATH
+        # This executes in the shell, expands $(pwd),
+        # and saves it for all following steps.
+        run: |
+          echo "PYTHONPATH=$(pwd)/modules" >> $GITHUB_ENV
       - name: Build HTML Assets
         # working-directory: notebooks/
-        env:
-          PYTHONPATH: $(pwd)/modules
         run: |
           source venv/bin/activate
           npx myst build --execute --html