presto-main/src/main/java/io/prestosql/execution/RevokeTask.java/RevokeTask/parsePrivilege
class RevokeTask:    private static Privilege parsePrivilege(Revoke statement, String privilegeString)
    {
        for (Privilege privilege : Privilege.values()) {
            if (privilege.name().equalsIgnoreCase(privilegeString)) {
                return privilege;
            }
        }

        throw semanticException(INVALID_PRIVILEGE, statement, "Unknown privilege: '%s'", privilegeString);
    }