Merge branch '5.2' into 5.3

* 5.2:
  fix tests (ter)
  Fix tests (bis)
  [travis] fix travis hopefuly
  [Security] Fix SerializableUser fixture
  [FrameworkBundle][WebProfilerBundle] Don't pass null to string parameters

Author: nicolas-grekas

Tests/Authentication/Token/AbstractTokenTest.php

@@ -278,12 +278,22 @@ public function getSalt()
 
     public function serialize(): string
     {
-        return serialize($this->name);
+        return serialize($this->__serialize());
     }
 
     public function unserialize($serialized): void
     {
-        $this->name = unserialize($serialized);
+        $this->__unserialize(unserialize($serialized));
+    }
+
+    public function __serialize(): array
+    {
+        return ['name' => $this->name];
+    }
+
+    public function __unserialize(array $data): void
+    {
+        ['name' => $this->name] = $data;
     }
 }