```psql
DBNAME=# \du
                                    List of roles
  Role name  |                         Attributes                         | Member of
-------------+------------------------------------------------------------+-----------
 user        |                                                            | {}
 postgres    | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
 dbuser      |                                                            | {}

DBNAME=# REASSIGN OWNED BY dbuser TO postgres;
REASSIGN OWNED
DBNAME=# REVOKE ALL PRIVILEGES ON ALL TABLES IN SCHEMA public FROM dbuser;
REVOKE
DBNAME=# REVOKE ALL PRIVILEGES ON ALL FUNCTIONS IN SCHEMA public FROM dbuser;
REVOKE
DBNAME=# REVOKE ALL PRIVILEGES ON ALL SEQUENCES IN SCHEMA public FROM dbuser;
REVOKE
DBNAME=# REVOKE ALL PRIVILEGES ON ALL TABLES IN SCHEMA public FROM dbuser;
REVOKE
DBNAME=# DROP USER dbuser;
ERROR:  role "dbuser" cannot be dropped because some objects depend on it
DETAIL:  privileges for database DBNAME
DBNAME=# REVOKE ALL PRIVILEGES ON DATABASE DBNAME FROM dbuser;
ERROR:  database "remocao" does not exist
DBNAME=# REVOKE ALL PRIVILEGES ON DATABASE "DBNAME" FROM dbuser;
REVOKE
DBNAME=# DROP USER dbuser;
DROP ROLE
```