ci(nightly_detect_failure): add actionable message in case of failure (…

…#17329)

Also, remove the logic that detects whether a message has already been
posted, since we now post the sha which is always different.

.github/workflows/nightly_detect_failure.yml

@@ -23,6 +23,7 @@ jobs:
         topic: 'Mathlib status updates'
         content: |
           ❌ The latest CI for Mathlib's branch#nightly-testing has [failed](https://github.com/${{ github.repository }}/actions/runs/${{ github.event.workflow_run.id }}) ([${{ github.sha }}](https://github.com/${{ github.repository }}/commit/${{ github.sha }})).
+          You can `git fetch; git checkout nightly-testing` and push a fix.
 
   handle_success:
     if: ${{ github.event.workflow_run.conclusion == 'success' && github.event.workflow_run.head_branch == 'nightly-testing' }}
@@ -211,25 +212,14 @@ jobs:
             payload = f"🛠️: it looks like it's time to create a new bump/nightly-{current_version} branch from nightly-testing (specifically {sha}), and then PR that to {bump_branch}. "
             payload += "To do so semi-automatically, run the following script from mathlib root:\n\n"
             payload += f"```bash\n./scripts/create-adaptation-pr.sh --bumpversion={bump_branch_suffix} --nightlydate={current_version} --nightlysha={sha}\n```\n"
-            # Only post if the message is different
-            # We compare the first 160 characters, since that includes the date and bump version
-            if not messages or messages[0]['content'][:160] != payload[:160]:
-                # Log messages, because the bot seems to repeat itself...
-                if messages:
-                    print("###### Last message:")
-                    print(messages[0]['content'])
-                    print("###### Current message:")
-                    print(payload)
-                else:
-                    print('The strings match!')
-                # Post the reminder message
-                request = {
-                    'type': 'stream',
-                    'to': 'nightly-testing',
-                    'topic': 'Mathlib bump branch reminders',
-                    'content': payload
-                }
-                result = client.send_message(request)
-                print(result)
+            # Post the reminder message
+            request = {
+                'type': 'stream',
+                'to': 'nightly-testing',
+                'topic': 'Mathlib bump branch reminders',
+                'content': payload
+            }
+            result = client.send_message(request)
+            print(result)
         else:
             print('No action needed.')