$ php bin/console server:run [Symfony\Component\Config\Definition\Exception\InvalidConfigurationException] The child node "db_driver" at path "fos_user" must be configured.必须新建一个USer类
[Symfony\Component\Config\Definition\Exception\InvalidConfigurationException] The child node "db_driver" at path "fos_user" must be configured.
原文：http://www.cnblogs.com/Amos-Turing/p/6731191.html
