minor #24604 Fix deprecation triggering test deduction (alexpott)

This PR was merged into the 3.3 branch.

Discussion
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Fix deprecation triggering test deduction

| Q             | A
| ------------- | ---
| Branch?       | 3.3
| Bug fix?      | yes
| New feature?  | no <!-- don't forget to update src/**/CHANGELOG.md files -->
| BC breaks?    | no
| Deprecations? | no <!-- don't forget to update UPGRADE-*.md files -->
| Tests pass?   | yes
| Fixed tickets | #... <!-- #-prefixed issue number(s), if any -->
| License       | MIT
| Doc PR        | symfony/symfony-docs#... <!--highly recommended for new features-->

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- Bug fixes must be submitted against the lowest branch where they apply
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- Features and deprecations must be submitted against the 3.4,
  legacy code removals go to the master branch.
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This PR is just testing some additions https://github.com/symfony/symfony/pull/24597 - I want to see if the travis run is successful.

Commits
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5333680 Fix review points

src/Symfony/Bridge/PhpUnit/Legacy/SymfonyTestsListenerTrait.php

@@ -326,6 +326,12 @@ class SymfonyTestsListenerTrait
 
             return $h ? $h($type, $msg, $file, $line, $context) : false;
         }
+        // If the message is serialized we need to extract the message. This occurs when the error is triggered by
+        // by the isolated test path in \Symfony\Bridge\PhpUnit\Legacy\SymfonyTestsListenerTrait::endTest().
+        $parsedMsg = @unserialize($msg);
+        if (is_array($parsedMsg)) {
+            $msg = $parsedMsg['deprecation'];
+        }
         if (error_reporting()) {
             $msg = 'Unsilenced deprecation: '.$msg;
         }