MAINT: update cache script to fail for execution error

Author: mmcky

.github/workflows/cache.yml

@@ -34,7 +34,13 @@ jobs:
       - name: Build HTML
         shell: bash -l {0}
         run: |
-          jb build lectures --path-output ./
+          jb build lectures --path-output ./ -W --keep-going
+      - name: Upload Execution Reports
+        uses: actions/upload-artifact@v2
+        if: failure()
+        with:
+          name: execution-reports
+          path: _build/html/reports
       - name: Upload "_build" folder (cache)
         uses: actions/upload-artifact@v2
         with: