Merge branch '5.1' into 5.2

* 5.1:
  remove unreachable code
  Update ExceptionEvent.php
  fix firebase transport factory DI tag type
  [HttpFoundation] Fix for virtualhosts based on URL path

Author: derrabus

Diff for: Resources/config/notifier_transports.php

@@ -73,7 +73,7 @@
 
         ->set('notifier.transport_factory.firebase', FirebaseTransportFactory::class)
             ->parent('notifier.transport_factory.abstract')
-            ->tag('texter.transport_factory')
+            ->tag('chatter.transport_factory')
 
         ->set('notifier.transport_factory.freemobile', FreeMobileTransportFactory::class)
             ->parent('notifier.transport_factory.abstract')