Fix deprecation for symfony/config 4.2+

Heavily inspired by symfony/maker-bundle#324

Author: bits4breakfast

src/DependencyInjection/Configuration.php

@@ -10,8 +10,13 @@ class Configuration implements ConfigurationInterface
 {
     public function getConfigTreeBuilder()
     {
-        $treeBuilder = new TreeBuilder;
-        $treeBuilder->root('aws', 'variable');
+        // Most recent versions of TreeBuilder have a constructor
+        if (\method_exists(TreeBuilder::class, '__construct')) {
+            $treeBuilder = new TreeBuilder('aws', 'variable');
+        } else { // which is not the case for older versions
+            $treeBuilder = new TreeBuilder;
+            $treeBuilder->root('aws', 'variable');
+        }
 
         return $treeBuilder;
     }