expose permission exceptions to the API

lib/Controller.php

@@ -196,6 +196,7 @@ class Controller
      */
     private function _create()
     {
+        try {
             // Ensure last paste from visitors IP address was more than configured amount of seconds ago.
             TrafficLimiter::setConfiguration($this->_conf);
             if (!TrafficLimiter::canPass()) {
@@ -207,6 +208,10 @@ class Controller
                 );
                 return;
             }
+        } catch (Exception $e) {
+            $this->_return_message(1, I18n::_($e->getMessage()));
+            return;
+        }
 
         $data      = $this->_request->getData();
         $isComment = array_key_exists('pasteid', $data) &&