create table emp(empid number,ename varchar2(10),deptno number)

CREATE OR REPLACE FUNCTION no_dept10(
      p_schema  IN VARCHAR2,
      p_object  IN VARCHAR2)
      RETURN VARCHAR2
    AS
    BEGIN
      RETURN 'deptno != 10';
    END;

Grant select on emp to X1;

SQL> BEGIN
  2        DBMS_RLS.add_policy
  3           (object_schema    => 'X1',
  4            object_name      => 'EMP',
  5            policy_name      => 'quickstart',
  6            policy_function  => 'no_dept10');
  7      END;
  8  /

BEGIN
      DBMS_RLS.add_policy
         (object_schema    => 'X1',
          object_name      => 'EMP',
          policy_name      => 'quickstart',
          policy_function  => 'no_dept10');
    END;

ORA-00942: table or view does not exist
ORA-06512: at "SYS.DBMS_RLS", line 20
ORA-06512: at line 2