there exists a race condition that can break replication when dropping a user.
Ideally one would use the "sql_log_bin: no" option to avoid this but
that is not possible on Google CloudSQL instances. Adding IF EXISTS
clause to the DROP USER statement makes it replication safe without
the need to skip logging.
* Remove all code related to VALID_PRIVS and get_valid_privs()
* Add tests to update user with invalid privs
* Re-raise InvalidPrivsError when granting privileges
* Fix: compatibility with python2
* More explicit assertions as commented by Andersson007
* Add changelog fragment
* mysql_user: replace VALID_PRIVS by get_valid_privs() function
* Add EXTRA_PRIVS in case we need to add more privs in the future
* Add changelog fragment
