fix deprecation notice

Author: OxCom

DependencyInjection/Configuration.php

@@ -61,8 +61,14 @@ class Configuration implements ConfigurationInterface
      */
     public function getConfigTreeBuilder()
     {
-        $treeBuilder      = new TreeBuilder();
-        $rootNode         = $treeBuilder->root(SymfonyRollbarExtension::ALIAS);
+        if (method_exists(TreeBuilder::class, 'getRootNode')) {
+            $treeBuilder = new TreeBuilder(SymfonyRollbarExtension::ALIAS);
+            $rootNode = $treeBuilder->getRootNode();
+        } else {
+            $treeBuilder = new TreeBuilder();
+            $rootNode    = $treeBuilder->root(SymfonyRollbarExtension::ALIAS);
+        }
+
         $defaultErrorMask = E_ERROR | E_WARNING | E_PARSE | E_CORE_ERROR | E_USER_ERROR | E_RECOVERABLE_ERROR;
 
         $rootNode

composer.json

@@ -30,7 +30,7 @@
     "require": {
         "php": ">=5.6",
         "monolog/monolog": "^1.23",
-        "rollbar/rollbar": "^1.3",
+        "rollbar/rollbar": "^1.6",
         "symfony/dependency-injection": "^2.8|~3.0|~4.0",
         "symfony/config": "^2.8|~3.0|~4.0",
         "symfony/http-kernel": "^2.8|~3.0|~4.0",