#10611 Ignore request key check for error page to avoid redirect loop

Author: Lukasz Bajsarowicz

app/code/Magento/Backend/Controller/Adminhtml/Noroute/Index.php

@@ -39,4 +39,14 @@ public function execute()
         $resultPage->addHandle('adminhtml_noroute');
         return $resultPage;
     }
+
+    /**
+     * Error page should be public accessible. Do not check keys to avoid redirect loop
+     *
+     * @return bool
+     */
+    protected function _validateSecretKey()
+    {
+        return true;
+    }
 }