add throws tags doc block for Twig_Environment:load

lib/Twig/Environment.php

@@ -383,6 +383,10 @@ class Twig_Environment
      *
      * @param string|Twig_TemplateWrapper|Twig_Template $name The template name
      *
+     * @throws Twig_Error_Loader  When the template cannot be found
+     * @throws Twig_Error_Runtime When a previously generated cache is corrupted
+     * @throws Twig_Error_Syntax  When an error occurred during compilation
+     *
      * @return Twig_TemplateWrapper
      */
     public function load($name)