Code:
CREATE OR REPLACE function  user_drop (p_user   in   text)
returns setof record  AS $BODY$ 
DECLARE
   sql_new_statement text;
    cur_user_roles CURSOR(p_user  text)
      for    select 'revoke '||c.rolname||' from '||a.rolname||';'
              from pg_catalog.pg_roles a
              inner join pg_auth_members b on a.oid=b.member
              inner join pg_roles c on b.roleid=c.oid
...