Merge branch '5.2' into 5.3

* 5.2:
  Do not use static::class for final messages
  prevent reflection usages when classes do not exist
  [HttpFoundation] allow savePath of NativeFileSessionHandler to be null

Author: derrabus

Message/EmailMessage.php

@@ -37,7 +37,7 @@ public function __construct(RawMessage $message, Envelope $envelope = null)
     public static function fromNotification(Notification $notification, EmailRecipientInterface $recipient): self
     {
         if ('' === $recipient->getEmail()) {
-            throw new InvalidArgumentException(sprintf('"%s" needs an email, it cannot be empty.', static::class));
+            throw new InvalidArgumentException(sprintf('"%s" needs an email, it cannot be empty.', __CLASS__));
         }
 
         if (!class_exists(NotificationEmail::class)) {

Message/SmsMessage.php

@@ -27,7 +27,7 @@ final class SmsMessage implements MessageInterface
     public function __construct(string $phone, string $subject)
     {
         if ('' === $phone) {
-            throw new InvalidArgumentException(sprintf('"%s" needs a phone number, it cannot be empty.', static::class));
+            throw new InvalidArgumentException(sprintf('"%s" needs a phone number, it cannot be empty.', __CLASS__));
         }
 
         $this->subject = $subject;