Creating user using procedure

Hello All,

I'm trying to create and assign the required roles to the user using a stored procedure compilled in another user.

For example I have complied the below procedure in the user "parent" , when i call this procedure to create another user/ schema in the database the script fails with error messge "ORA-01935: missing user or role name"

Please note that user Parent has been graned all the below permission and create user and drop user privileges.

Procedure :

create or replace procedure cr_user (user_name in varchar2) is

out_username varchar2(300);
begin
execute immediate 'create user '||out_username||' identified by '||out_username||' default tablespace usr temporary tablespace temporary';