Throw an exception is expression language is not installed

Author: sroze

src/Symfony/Component/DependencyInjection/Compiler/AnalyzeServiceReferencesPass.php

@@ -14,6 +14,7 @@
 use Symfony\Component\DependencyInjection\Argument\ArgumentInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\DependencyInjection\Definition;
+use Symfony\Component\DependencyInjection\Exception\RuntimeException;
 use Symfony\Component\DependencyInjection\ExpressionLanguage;
 use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
@@ -155,6 +156,10 @@ private function getDefinitionId($id)
     private function getExpressionLanguage()
     {
         if (null === $this->expressionLanguage) {
+            if (!class_exists('Symfony\Component\ExpressionLanguage\ExpressionLanguage')) {
+                throw new RuntimeException('Unable to use expressions as the Symfony ExpressionLanguage component is not installed.');
+            }
+
             $providers = $this->container->getExpressionLanguageProviders();
             $this->expressionLanguage = new ExpressionLanguage(null, $providers, function ($arg) {
                 if ('""' === substr_replace($arg, '', 1, -1)) {