minor symfony#30679 [Messenger] Add missing information in messenger logs (fabpot)

This PR was merged into the 4.3-dev branch.

Discussion
----------

[Messenger] Add missing information in messenger logs

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | yes-ish
| New feature?  | yes-ish
| BC breaks?    | no
| Deprecations? | no <!-- don't forget to update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

When using `messenger:consume`, I get the following logs:

```
2019-03-25T11:39:05+01:00 [info] Received message "Symfony\Component\Mailer\EnvelopedMessage"
2019-03-25T11:39:05+01:00 [warning] An exception occurred while handling message "Symfony\Component\Mailer\EnvelopedMessage"
2019-03-25T11:39:05+01:00 [info] Retrying Symfony\Component\Mailer\EnvelopedMessage - retry #1.
2019-03-25T11:39:05+01:00 [info] Sending message "Symfony\Component\Mailer\EnvelopedMessage" with "Symfony\Component\Messenger\Transport\AmqpExt\AmqpTransport"
2019-03-25T11:39:06+01:00 [info] Received message "Symfony\Component\Mailer\EnvelopedMessage"
2019-03-25T11:39:06+01:00 [warning] An exception occurred while handling message "Symfony\Component\Mailer\EnvelopedMessage"
2019-03-25T11:39:06+01:00 [info] Retrying Symfony\Component\Mailer\EnvelopedMessage - retry #2.
2019-03-25T11:39:06+01:00 [info] Sending message "Symfony\Component\Mailer\EnvelopedMessage" with "Symfony\Component\Messenger\Transport\AmqpExt\AmqpTransport"
2019-03-25T11:39:09+01:00 [info] Received message "Symfony\Component\Mailer\EnvelopedMessage"
2019-03-25T11:39:09+01:00 [warning] An exception occurred while handling message "Symfony\Component\Mailer\EnvelopedMessage"
2019-03-25T11:39:09+01:00 [info] Retrying Symfony\Component\Mailer\EnvelopedMessage - retry #3.
2019-03-25T11:39:09+01:00 [info] Sending message "Symfony\Component\Mailer\EnvelopedMessage" with "Symfony\Component\Messenger\Transport\AmqpExt\AmqpTransport"
```

So, an. error occurred, but I have no idea what's going on. The exception is in the context, but the context is not displayed by default. So, this PR fixes it.

Commits
-------

20664ca [Messenger] added missing information in messenger logs

Author: fabpot

src/Symfony/Component/Messenger/Middleware/LoggingMiddleware.php

@@ -46,7 +46,7 @@ public function handle(Envelope $envelope, StackInterface $stack): Envelope
             $envelope = $stack->next()->handle($envelope, $stack);
         } catch (\Throwable $e) {
             $context['exception'] = $e;
-            $this->logger->warning('An exception occurred while handling message "{class}"', $context);
+            $this->logger->warning('An exception occurred while handling message "{class}": '.$e->getMessage(), $context);
 
             throw $e;
         }

src/Symfony/Component/Messenger/Middleware/SendMessageMiddleware.php

@@ -91,7 +91,7 @@ public function handle(Envelope $envelope, StackInterface $stack): Envelope
             }
         } catch (\Throwable $e) {
             $context['exception'] = $e;
-            $this->logger->warning('An exception occurred while handling message "{class}"', $context);
+            $this->logger->warning('An exception occurred while handling message "{class}": '.$e->getMessage(), $context);
 
             throw $e;
         }