How to copy user rights and roles from one user to another I require a PL/SQL script that copies all of a user's rights, roles and mandates from one user to another.  

I am using Oracle 12c.
may be helpful.

SELECT DBMS_METADATA.GET_GRANTED_DDL('ROLE_GRANT','username') FROM DUAL;
SELECT DBMS_METADATA.GET_GRANTED_DDL('SYSTEM_GRANT','username') FROM DUAL;

set long 9999999
SELECT DBMS_METADATA.GET_GRANTED_DDL('OBJECT_GRANT','username') FROM DUAL;