title: How to revoke and grant permissions to a user with GCP's new managed MySQL 8.0
body: <p>I had no problems making a test MySQL server and applying permissions a week ago with their MySQL 5.7, but trying out the new 8.0 version, I can't seem to alter permissions as easily, if at all. I'm logged in as root remotely, but a local cloud shell instance does the same.</p>
  <p>I'm trying to create a new user that only has access to one database, but I can't seem to get past the part where I revoke all default permissions first.</p>
  <p>My method:</p>
  <p><code>CREATE USER 'test_user'@'%' IDENTIFIED BY '{password}';</code></p>
  <p>Gives no error. (I've also tried creating a user through GCP's admin panel)</p>
  <p><code>SHOW GRANTS FOR 'test_user'@'%';</code> returns <code>GRANT USAGE ON *.* TO `test_user`@`%` </code> (I assume this means the new user has full permissions?)</p>
  <p>Then, trying to remove all privileges to start fresh with the user,</p>
  <p><code>REVOKE ALL PRIVILEGES, GRANT OPTION FROM 'test_user'@'%';</code></p>
  <p>shows:</p>
  <p><code>Error: UNKNOWN_CODE_PLEASE_REPORT: Access denied for AuthId `root`@`%` to database 'mysql'.</code></p>
  <p>I'm pretty new to Mysql, so I'm unsure if this is my fault or just a bug. Thank you!</p>