[FrameworkBundle] changed error_log() calls to logger calls

src/Symfony/Bundle/FrameworkBundle/Controller/ExceptionListener.php

@@ -70,9 +70,13 @@ class ExceptionListener
         try {
             $response = $event->getSubject()->handle($request, HttpKernelInterface::SUB_REQUEST, true);
 
-            error_log(sprintf('%s: %s', get_class($exception), $exception->getMessage()));
+            if (null !== $this->logger) {
+                $this->logger->err(sprintf('%s: %s', get_class($exception), $exception->getMessage()));
+            }
         } catch (\Exception $e) {
-            error_log(sprintf('Exception thrown when handling an exception (%s: %s)', get_class($e), $e->getMessage()));
+            if (null !== $this->logger) {
+                $this->logger->err(sprintf('Exception thrown when handling an exception (%s: %s)', get_class($e), $e->getMessage()));
+            }
 
             return false;
         }