Automatically create an issue if the nightly stubtest run fails (#6978)

Co-authored-by: Nikita Sobolev <mail@sobolevn.me>

.github/workflows/stubtest.yml

@@ -5,6 +5,7 @@ on:
   schedule:
     - cron: "0 0 * * *"
 
+# Please keep the permissions minimal, as stubtest runs arbitrary code from pypi.
 permissions:
   contents: read
 
@@ -57,3 +58,23 @@ jobs:
         run: sudo apt install -y $(python tests/get_apt_packages.py)
       - name: Run stubtest
         run: python tests/stubtest_third_party.py --num-shards 4 --shard-index ${{ matrix.shard-index }}
+
+  # https://github.community/t/run-github-actions-job-only-if-previous-job-has-failed/174786/2
+  create-issue-on-failure:
+    name: Create an issue if stubtest failed
+    runs-on: ubuntu-latest
+    needs: [stubtest-stdlib, stubtest-third-party]
+    if: ${{ github.repository == 'python/typeshed' && always() && (needs.stubtest-stdlib.result == 'failure' || needs.stubtest-third-party.result == 'failure') }}
+    permissions:
+      issues: write
+    steps:
+      - uses: actions/github-script@v3
+        with:
+          github-token: ${{secrets.GITHUB_TOKEN}}
+          script: |
+            await github.issues.create({
+              owner: "python",
+              repo: "typeshed",
+              title: `Stubtest failed on ${new Date().toDateString()}`,
+              body: "Stubtest runs are listed here: https://github.com/python/typeshed/actions/workflows/stubtest.yml",
+            })