Several optimizations:

* Use `yield from` wherever appropriate.
* Use SA's .one_or_none() where appropriate.

- Fix a bug in MailingList.pass_extensions.
- Use ValueError in other places for consistency.
- Remove unreached/nonsense code.
- Simplify the SubscriptionService.find_member() and .find_members()
  implementations.
- Boost coverage.

2 files changed, 2 insertions, 4 deletions

diff --git a/src/mailman/testing/helpers.py b/src/mailman/testing/helpers.py
index ea940dbcf..fa16c1f7f 100644
--- a/src/mailman/testing/helpers.py
+++ b/src/mailman/testing/helpers.py
@@ -220,8 +220,7 @@ class TestableMaster(Master):
     @property
     def runner_pids(self):
         """The pids of all the child runner processes."""
-        for pid in self._started_kids:
-            yield pid
+        yield from self._started_kids
 
 
 
diff --git a/src/mailman/testing/mta.py b/src/mailman/testing/mta.py
index a75e49237..9642803e2 100644
--- a/src/mailman/testing/mta.py
+++ b/src/mailman/testing/mta.py
@@ -251,8 +251,7 @@ class ConnectionCountingController(QueueController):
     @property
     def messages(self):
         """Return all the messages received by the SMTP server."""
-        for message in self:
-            yield message
+        yield from self
 
     def clear(self):
         """Clear all the messages from the queue."""