Improve exception thrown when user does not exists

The previous exception was Runtime; since attackers perform batch requests on this services with random emails, logs systems gets flooded with "User not found" messages, which are not useful for debugging since this is not a runtime exception as is.

Author: Eseperio

src/User/Service/PasswordRecoveryService.php

@@ -50,7 +50,7 @@ public function run()
             $user = $this->query->whereEmail($this->email)->one();
 
             if ($user === null) {
-                throw new \RuntimeException('User not found.');
+                throw new NotFoundHttpException(Yii::t('usuario', 'User not found'));
             }
 
             $token = TokenFactory::makeRecoveryToken($user->id);