How to get response message

I am want to delete old records using function so my senior has function like below but I want to get response of this particular inside query wheter it is successful or failure

How to get response of the function status

 create or replace function data_purge() returns void as$$

Declare

Begin

Drop table test_old;

Create table test_old as select * from sales where bill_date<now() -interval '1 year';

Delete table sales where sales_id in (select sales_id from test_old;

End;

$$ language plpgsql;