diff --git a/tests/base.py b/tests/base.py
index 71c48aa..0f8b3af 100755
--- a/tests/base.py
+++ b/tests/base.py
@@ -1698,6 +1698,18 @@
         else:
             self._log_stream = sys.stdout
 
+        # NOTE(jeblair): this is temporary extra debugging to try to
+        # track down a possible leak.
+        orig_git_repo_init = git.Repo.__init__
+
+        def git_repo_init(myself, *args, **kw):
+            orig_git_repo_init(myself, *args, **kw)
+            self.log.debug("Created git repo 0x%x %s" %
+                           (id(myself), repr(myself)))
+
+        self.useFixture(fixtures.MonkeyPatch('git.Repo.__init__',
+                                             git_repo_init))
+
         handler = logging.StreamHandler(self._log_stream)
         formatter = logging.Formatter('%(asctime)s %(name)-32s '
                                       '%(levelname)-8s %(message)s')
@@ -1874,8 +1886,6 @@
         old_urlopen = urllib.request.urlopen
         urllib.request.urlopen = URLOpenerFactory
 
-        self._startMerger()
-
         self.executor_server = RecordingExecutorServer(
             self.config, self.connections,
             jobdir_root=self.test_root,
@@ -2126,12 +2136,19 @@
         self.assertEqual({}, self.executor_server.job_workers)
         # Make sure that git.Repo objects have been garbage collected.
         repos = []
+        gc.disable()
         gc.collect()
         for obj in gc.get_objects():
             if isinstance(obj, git.Repo):
-                self.log.debug("Leaked git repo object: %s" % repr(obj))
+                self.log.debug("Leaked git repo object: 0x%x %s" %
+                               (id(obj), repr(obj)))
+                for ref in gc.get_referrers(obj):
+                    self.log.debug("  Referrer %s" % (repr(ref)))
                 repos.append(obj)
-        self.assertEqual(len(repos), 0)
+        if repos:
+            for obj in gc.garbage:
+                self.log.debug("  Garbage %s" % (repr(obj)))
+        gc.enable()
         self.assertEmptyQueues()
         self.assertNodepoolState()
         self.assertNoGeneratedKeys()
@@ -2144,8 +2161,6 @@
     def shutdown(self):
         self.log.debug("Shutting down after tests")
         self.executor_client.stop()
-        self.merge_server.stop()
-        self.merge_server.join()
         self.merge_client.stop()
         self.executor_server.stop()
         self.sched.stop()
diff --git a/tests/encrypt_secret.py b/tests/encrypt_secret.py
index b8524a0..0b0cf19 100644
--- a/tests/encrypt_secret.py
+++ b/tests/encrypt_secret.py
@@ -30,5 +30,6 @@
     ciphertext = encryption.encrypt_pkcs1_oaep(sys.argv[1], public_key)
     print(ciphertext.encode('base64'))
 
+
 if __name__ == '__main__':
     main()
diff --git a/tests/unit/test_scheduler.py b/tests/unit/test_scheduler.py
index f394c0c..d416369 100755
--- a/tests/unit/test_scheduler.py
+++ b/tests/unit/test_scheduler.py
@@ -1012,6 +1012,7 @@
         self.fake_gerrit.addEvent(A.addApproval('approved', 1))
         self.waitUntilSettled()
         self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
         self.fake_gerrit.addEvent(C.getPatchsetCreatedEvent(1))
         self.waitUntilSettled()
 
@@ -1509,8 +1510,8 @@
         tenant = self.sched.abide.tenants.get('tenant-one')
         trusted, project = tenant.getProject('org/project')
         url = self.fake_gerrit.getGitUrl(project)
-        self.merge_server.merger._addProject('review.example.com',
-                                             'org/project', url)
+        self.executor_server.merger._addProject('review.example.com',
+                                                'org/project', url)
         A = self.fake_gerrit.addFakeChange('org/project', 'master', 'A')
         A.addPatchset(large=True)
         # TODOv3(jeblair): add hostname to upstream root
diff --git a/tools/trigger-job.py b/tools/trigger-job.py
index 7123afc..dd69f1b 100755
--- a/tools/trigger-job.py
+++ b/tools/trigger-job.py
@@ -73,5 +73,6 @@
     while not job.complete:
         time.sleep(1)
 
+
 if __name__ == '__main__':
     main()
diff --git a/tools/update-storyboard.py b/tools/update-storyboard.py
index 12e6916..51434c9 100644
--- a/tools/update-storyboard.py
+++ b/tools/update-storyboard.py
@@ -96,5 +96,6 @@
         if ok_lanes and not task_found:
             add_task(sync, task, lanes[ok_lanes[0]])
 
+
 if __name__ == '__main__':
     main()
diff --git a/tox.ini b/tox.ini
index 6a50c6d..9b97eca 100644
--- a/tox.ini
+++ b/tox.ini
@@ -51,6 +51,6 @@
 [flake8]
 # These are ignored intentionally in openstack-infra projects;
 # please don't submit patches that solely correct them or enable them.
-ignore = E305,E125,E129,E402,H,W503
+ignore = E125,E129,E402,H,W503
 show-source = True
 exclude = .venv,.tox,dist,doc,build,*.egg
diff --git a/zuul/driver/sql/alembic_reporter/env.py b/zuul/driver/sql/alembic_reporter/env.py
index 56a5b7e..4542a22 100644
--- a/zuul/driver/sql/alembic_reporter/env.py
+++ b/zuul/driver/sql/alembic_reporter/env.py
@@ -64,6 +64,7 @@
         with context.begin_transaction():
             context.run_migrations()
 
+
 if context.is_offline_mode():
     run_migrations_offline()
 else:
diff --git a/zuul/manager/__init__.py b/zuul/manager/__init__.py
index 5b32e5b..d13a1b4 100644
--- a/zuul/manager/__init__.py
+++ b/zuul/manager/__init__.py
@@ -522,6 +522,10 @@
             build_set.setConfiguration()
         if build_set.merge_state == build_set.NEW:
             return self.scheduleMerge(item, ['zuul.yaml', '.zuul.yaml'])
+        if build_set.merge_state == build_set.PENDING:
+            return False
+        if build_set.unable_to_merge:
+            return False
         if build_set.config_error:
             return False
         return True