PDOException: SQLSTATE  Access denied for user 'db_user'@'localhost' to database 'dbname' in lock_may_be_available() (line
167 of /home/user/public_html/includes/lock.inc).
The username and password were correct but some reason CPanel added the user with no permissions! Edit the user's permissions to include "All" from Cpanel or MySQL and that is the solution.
drupal, mysql, database, pdoexception, sqlstate, user, db_user, localhost, dbname, lock_may_be_available, public_html, includes, inc, username, password, cpanel, permissions, edit, quot,