在Google Cloud SQL上建立数据库连接时出错

Question

按照Google App Engine创建本地WordPress开发平台的说明，我使用指令的MySQL方向创建了数据库和初始用户：

我在SQL上创建了一个用户，创建了实例，允许访问但我一直收到错误

Error establishing a database connection

以下是我的wp-config.php文件：

if (isset($_SERVER['SERVER_SOFTWARE']) && strpos($_SERVER['SERVER_SOFTWARE'], 'Google App Engine') !== false) {
    /** The name of the Cloud SQL database for WordPress */
    define('DB_NAME', 'wordpresstest');
    /** Live environment Cloud SQL login and SITE_URL info */
    /** Note that from App Engine, the password is not required, so leave it blank here */
    define('DB_HOST', ':/cloudsql/wordpresstest-1382:wordpresstest');
    define('DB_USER', 'root');
    define('DB_PASSWORD', '');
} else {
    /** The name of the local database for WordPress */
    define('DB_NAME', 'wordpresstest');
    /** Local environment MySQL login info */
    define('DB_HOST', 'localhost');
    define('DB_USER', 'root');
    define('DB_PASSWORD', '');
}

以下是我的app.yaml文件：

# [START env]
env_variables:
  # Replace project, instance, database, user and password with the values obtained
  # when configuring your Cloud SQL instance.
  MYSQL_DSN: mysql:unix_socket=/cloudsql/wordpresstest-1382:wordpresstest;dbname=wordpresstest
  MYSQL_USER: root
  MYSQL_PASSWORD: ''
# [END env]

当我在Google Cloud Launcher上运行localhost时，仍然会收到错误。