Update docs.yml

Author: kayjan

.github/workflows/docs.yml

@@ -11,6 +11,9 @@ jobs:
   docs:
     runs-on: ubuntu-latest
     steps:
+      - name: Check if upstream workflow failed
+        if: ${{ github.event.workflow_run.conclusion == 'failure' }}
+        run: exit 1
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2
       - name: Install dependencies