"Error establishing a database connection" Wordpress and Google App Engine

[CyberBurst via StackOverflow]

I have been trying to follow this tutorial on launching a wordpress site using google app engine. I have the site deployed and I created a SQL instance on the site project, but the site apparently doesn't see the instance. In the tutorial it says to input this command into the MySQL Command Line Client:

{PATH_TO_MYSQL_BIN}/mysql --host=INSTANCE_IP --user=root --password
create database wordpress_db;
exit;

And whenever I do I get syntax errors. I don't know what it means by {PATH_TO_MYSQL_BIN}/mysql is that the path to my project folder? Or do I even need to use this command?

The SQL instance I set up on the Google Cloud Platform is a first generation. Shouldn't it automatically link the database to the project? And if so, why am I getting an error message?

My SQL instance name is wordpress-a and my project id is blendertrainer.

Here is my App.yaml:

application: blendertrainer
version: firstlaunching
runtime: php55
api_version: 1

handlers:
- url: /(.*\.(htm|html|css|js))$
  static_files: wordpress/\1
  upload: wordpress/.*\.(htm|html|css|js)$
  application_readable: true

- url: /wp-content/(.*\.(ico|jpg|jpeg|png|gif|woff|ttf|otf|eot|svg))$
  static_files: wordpress/wp-content/\1
  upload: wordpress/wp-content/.*\.(ico|jpg|jpeg|png|gif|woff|ttf|otf|eot|svg)$
  application_readable: true

- url: /(.*\.(ico|jpg|jpeg|png|gif|woff|ttf|otf|eot|svg))$
  static_files: wordpress/\1
  upload: wordpress/.*\.(ico|jpg|jpeg|png|gif|woff|ttf|otf|eot|svg)$
  application_readable: true

- url: /wp-includes/images/media/(.*\.(ico|jpg|jpeg|png|gif|woff|ttf|otf|eot|svg))$
  static_files: wordpress/wp-includes/images/media/\1
  upload: wordpress/wp-includes/images/media/.*\.(ico|jpg|jpeg|png|gif|woff|ttf|otf|eot|svg)$
  application_readable: true

- url: /wp-admin/(.+)
  script: wordpress/wp-admin/\1
  secure: always

- url: /wp-admin/
  script: wordpress/wp-admin/index.php
  secure: always

- url: /wp-login.php
  script: wordpress/wp-login.php
  secure: always

- url: /wp-cron.php
  script: wordpress/wp-cron.php
  login: admin

- url: /xmlrpc.php
  script: wordpress/xmlrpc.php

- url: /wp-(.+).php
  script: wordpress/wp-\1.php

- url: /(.+)?/?
  script: wordpress/index.php

skip_files:
- ^(.*/)?\.zip$
- ^(.*/)?\.bat$
- ^(.*/)?\.sh$
- ^(.*/)?\.md$

Here is my wp_config:

<?php
    /**
     * The base configurations of the WordPress.
     *
     * This file has the following configurations: MySQL settings, Table Prefix,
     * Secret Keys, WordPress Language, and ABSPATH. You can find more information
     * by visiting {@link http://codex.wordpress.org/Editing_wp-config.php Editing
     * wp-config.php} Codex page. You can get the MySQL settings from your web host.
     *
     * This file is used by the wp-config.php creation script during the
     * installation. You don't have to use the web site, you can just copy this file
     * to "wp-config.php" and fill in the values.
     *
     * @package WordPress
     */

    // Required for batcache use
    define('WP_CACHE', true);

    // ** MySQL settings - You can get this info from your web host ** //
    /** The name of the database for WordPress */
    define('DB_NAME', 'wordpress_db');

    if (isset($_SERVER['SERVER_SOFTWARE']) && strpos($_SERVER['SERVER_SOFTWARE'],'Google App Engine') !== false) {
        /** 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/blendertrainer:wordpress-a');
        define('DB_USER', 'root');
        define('DB_PASSWORD', '');
    } else {
        /** Local environment MySQL login info */
        define('DB_HOST', '127.0.0.1');
        define('DB_USER', 'root');
        define('DB_PASSWORD', '*********');
    }

    // Determine HTTP or HTTPS, then set WP_SITEURL and WP_HOME
    if (!empty($_SERVER['HTTPS']) && $_SERVER['HTTPS'] !== 'off' || $_SERVER['SERVER_PORT'] == 443)
    {
        $protocol_to_use = 'https://';
    } else {
        $protocol_to_use = 'http://';
    }
    define( 'WP_SITEURL', $protocol_to_use . $_SERVER['HTTP_HOST']);
    define( 'WP_HOME', $protocol_to_use . $_SERVER['HTTP_HOST']);

    /** Database Charset to use in creating database tables. */
    define('DB_CHARSET', 'utf8');

    /** The Database Collate type. Don't change this if in doubt. */
    define('DB_COLLATE', '');

    /**#@+
     * Authentication Unique Keys and Salts.
     *
     * Change these to different unique phrases!
     * You can generate these using the {@link https://api.wordpress.org/secret-key/1.1/salt/ WordPress.org secret-key service}
     * You can change these at any point in time to invalidate all existing cookies. This will force all users to have to log in again.
     *
     * @since 2.6.0
     */
    define('AUTH_KEY',         'put your unique phrase here');
    define('SECURE_AUTH_KEY',  'put your unique phrase here');
    define('LOGGED_IN_KEY',    'put your unique phrase here');
    define('NONCE_KEY',        'put your unique phrase here');
    define('AUTH_SALT',        'put your unique phrase here');
    define('SECURE_AUTH_SALT', 'put your unique phrase here');
    define('LOGGED_IN_SALT',   'put your unique phrase here');
    define('NONCE_SALT',       'put your unique phrase here');

    /**#@-*/

    /**
     * WordPress Database Table prefix.
     *
     * You can have multiple installations in one database if you give each a unique
     * prefix. Only numbers, letters, and underscores please!
     */
    $table_prefix  = 'wp_';

    /**
     * WordPress Localized Language, defaults to English.
     *
     * Change this to localize WordPress. A corresponding MO file for the chosen
     * language must be installed to wp-content/languages. For example, install
     * de_DE.mo to wp-content/languages and set WPLANG to 'de_DE' to enable German
     * language support.
     */
    define('WPLANG', '');

    /**
     * For developers: WordPress debugging mode.
     *
     * Change this to true to enable the display of notices during development.
     * It is strongly recommended that plugin and theme developers use WP_DEBUG
     * in their development environments.
     */
    define('WP_DEBUG', false);

    /**
     * Disable default wp-cron in favor of a real cron job
     */
    define('DISABLE_WP_CRON', true);

    // configures batcache
    $batcache = [
      'seconds'=>0,
      'max_age'=>30*60, // 30 minutes
      'debug'=>false
    ];
    /* That's all, stop editing! Happy blogging. */

    /** Absolute path to the WordPress directory. */
    if ( !defined('ABSPATH') )
        define('ABSPATH', dirname(__FILE__) . '/wordpress/');

    /** Sets up WordPress vars and included files. */
    require_once(ABSPATH . 'wp-settings.php');

Please DO NOT REPLY directly to this email but go to StackOverflow:
http://stackoverflow.com/questions/37867958/error-establishing-a-database-connection-wordpress-and-google-app-engine

[BrettJ via StackOverflow]

Your Cloud SQL instance needs authorize connections from your App Engine application.

1. In the Console, open the Cloud SQL instances page.
2. Click your SQL instance name.
3. Click the Access Control tab.
4. Click Add application ID and enter your project ID.

Please DO NOT REPLY directly to this email but go to StackOverflow:

http://stackoverflow.com/questions/37867958/error-establishing-a-database-connection-wordpress-and-google-app-engine/37871364#37871364