Merge branch '2.7' into 2.8

* 2.7:
  Show exception is checked twice in ExceptionController of twig
  allow SSI fragments configuration in XML files
  Display a better error message when the toolbar cannot be displayed
  render hidden _method field in form_rest()
  return fallback locales whenever possible

Author: xabbuh

DataCollectorTranslator.php

@@ -95,7 +95,7 @@ public function getCatalogue($locale = null)
      */
     public function getFallbackLocales()
     {
-        if ($this->translator instanceof Translator) {
+        if ($this->translator instanceof Translator || method_exists($this->translator, 'getFallbackLocales')) {
             return $this->translator->getFallbackLocales();
         }
 

LoggingTranslator.php

@@ -95,7 +95,7 @@ public function getCatalogue($locale = null)
      */
     public function getFallbackLocales()
     {
-        if ($this->translator instanceof Translator) {
+        if ($this->translator instanceof Translator || method_exists($this->translator, 'getFallbackLocales')) {
             return $this->translator->getFallbackLocales();
         }