Merge branch '6.3' into 6.4

* 6.3:
  fix typo
  CS fix
  [Serializer] Keep stack trace for enum value denormalizer error
  add the MailPace transport to the UnsupportedSchemeException
  [Serializer] Fix partial denormalization with missing constructor arguments
  [Serializer] Moves dummy to fixtures folder
  [HttpKernel] Don't validate partially denormalized object

Author: xabbuh

Tests/DependencyInjection/CompleteConfigurationTestCase.php

@@ -243,7 +243,7 @@ public function testFirewalls()
             ],
         ], $listeners);
 
-        $this->assertFalse($container->hasAlias(UserCheckerInterface::class, 'No user checker alias is registered when custom user checker services are registered'));
+        $this->assertFalse($container->hasAlias(UserCheckerInterface::class), 'No user checker alias is registered when custom user checker services are registered');
     }
 
     public function testFirewallRequestMatchers()