Error establishing a database connection on Google Cloud SQL - php

Question

Following Google App Engine's instructions for creating a local WordPress development platform, I created the database and initial user using the instruction's MySQL direction:
I have created a user on SQL, created instances, allowed access but I keep getting the error
Error establishing a database connection
Below is my wp-config.php file:
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', '');
}
Below is my app.yaml file:
# [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]
When I run localhost on Google Cloud Launcher, still getting the error.