Add GitHub Action to send email for Cirrus CI failures

.github/workflows/cirrus_email.yml

@@ -0,0 +1,26 @@
+name: Email about Cirrus CI failures
+
+on:
+  check_suite:
+    type: ['completed']
+
+jobs:
+  continue:
+    name: After Cirrus CI Failure
+    if: github.event.check_suite.app.name == 'Cirrus CI' && github.event.check_suite.conclusion != 'success'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: octokit/request-action@v2.x
+        id: get_failed_check_run
+        with:
+          route: GET /repos/${{ github.repository }}/check-suites/${{ github.event.check_suite.id }}/check-runs?status=completed
+          mediaType: '{"previews": ["antiope"]}'
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      - run: |
+          echo "Cirrus CI ${{ github.event.check_suite.conclusion }} on ${{ github.event.check_suite.head_branch }} branch!"
+          echo "SHA ${{ github.event.check_suite.head_sha }}"
+          echo $MESSAGE
+          echo "##[error]See $CHECK_RUN_URL for details" && false
+        env:
+          CHECK_RUN_URL: ${{ fromJson(steps.get_failed_check_run.outputs.data).check_runs[0].html_url }}