fixed error message parsing

@@ -21,7 +21,7 @@ exports = module.exports = function(logger, settings) {
 
       if (_.isObject(err) && _.isNumber(err.code) && err.code === 11000) {
         // <https://github.com/LearnBoost/mongoose/issues/2129>
-        var field = err.message.split('index: test.')[1].split('.$')[1]
+        var field = err.message.split('index: ')[1].split('.$')[1]
         // now we have `email_1 dup key`
         field = field.split(' dup key')[0]
         field = field.substring(0, field.lastIndexOf('_'))