Merge branch '4.4' into 5.2

* 4.4:
  [SecurityBundle] role_names variable instead of roles
  [PhpUnitBridge] fix reporting deprecations when they come from DebugClassLoader
  [ErrorHandler] fix parsing return types in DebugClassLoader
  [ErrorHandler] fix handling messages with null bytes from anonymous classes
  Restore priority for eventSubscribers

Author: nicolas-grekas

Tests/Authentication/Token/AbstractTokenTest.php

@@ -233,12 +233,12 @@ public function getSalt()
         return null;
     }
 
-    public function serialize()
+    public function serialize(): string
     {
         return serialize($this->name);
     }
 
-    public function unserialize($serialized)
+    public function unserialize($serialized): void
     {
         $this->name = unserialize($serialized);
     }