User, host, and privileges
USAGE = no privilege


https://dev.mysql.com/doc/refman/5.6/en/privileges-provided.html#priv_usage

Now you have to options, either delete the user or grant all privileges to the user, which ever make sense to you

CASE 1: If you want to remove 'foo'@'10.0.0.3'

REVOKE USAGE on *.* from 'foo'@'10.0.0.3' ;


will never work as there is no grant called USAGE So use 

DROP USER 'foo'@'10.0.0.3';


CASE 2: If you want to grant all privileges 'foo'@'10.0.0.3'

GRANT ALL PRIVILEGES ON *.* TO 'foo'@'10.0.0.3';
FLUSH PRIVILEGES;