for row in select loop question

The following function does not work:

CREATE FUNCTION InstallPermissions(varchar, varchar) RETURNS int2 AS '
DECLARE
options ALIAS FOR $1;
username ALIAS FOR $2;
BEGIN
FOR row IN select * from pg_tables LOOP
REVOKE ALL ON row.tablename FROM username;
GRANT options on row.tablename TO username;
END LOOP;
return 0;
END; ' LANGUAGE 'plpgsql';

"select InstallPermissions('test1', 'test2);" returns an error at "select".
Any suggestions on how to eliminate the error?

Thanks, Michael