[IMP] runbot_merge: send integratin failure comment via feedback queue

If a transient github failure makes the integration fail but also
makes the following reset fail the entire staging process would be
cancelled (and operations so far rollbacked) except for the failure
comment which would be effected, as in odoo/odoo#26380.

By pushing the comment to the feedback queue, if the reset fails the
comment is rollbacked and "unqueued".

runbot_merge/models/pull_requests.py

@@ -1313,7 +1313,11 @@ class Batch(models.Model):
             except (exceptions.MergeError, AssertionError) as e:
                 _logger.exception("Failed to merge %s:%s into staging branch (error: %s)", pr.repository.name, pr.number, e)
                 pr.state = 'error'
-                gh.comment(pr.number, "Unable to stage PR (%s)" % e)
+                self.env['runbot_merge.pull_requests.feedback'].create({
+                    'repository': pr.repository.id,
+                    'pull_request': pr.number,
+                    'message': "Unable to stage PR (%s)" % e,
+                })
 
                 # reset the head which failed, as rebase() may have partially
                 # updated it (despite later steps failing)

runbot_merge/tests/test_basic.py

@@ -652,6 +652,8 @@ def test_rebase_failure(env, repo, users, remote_p):
     with mock.patch.object(GH, 'set_ref', autospec=True, side_effect=wrapper) as m:
         env['runbot_merge.project']._check_progress()
 
+    env['runbot_merge.project']._send_feedback()
+
     assert pr_a.comments == [
         (users['reviewer'], 'hansen r+'),
         (users['user'], re_matches(r'^Unable to stage PR')),

runbot_merge/tests/test_multirepo.py

@@ -188,7 +188,7 @@ def test_merge_fail(env, project, repo_a, repo_b, users):
     pr2a = make_pr(repo_a, 'A2', [{'b': 'ok'}], label='do-b-thing')
     pr2b = make_pr(repo_b, 'B2', [{'b': 'ok'}], label='do-b-thing')
 
-    env['runbot_merge.project']._check_progress()
+    run_crons(env)
 
     s2 = to_pr(env, pr2a) | to_pr(env, pr2b)
     st = env['runbot_merge.stagings'].search([])