When trying to figure out why a function raised an exception you can print the error code raised to lookup in the table Appendix A-1.
One method is to capture others and then raise the magic sqlstate variable (only available in exception handlers)
create or replace function do_it(name text)
returns void
as $$
begin
select 42 from nothing;
exception
when others then
raise '%: %', sqlstate, sqlerrm;
end;
$$
security definer
language plpgsql
;
Then you can view the error:
select do_it('hi');
ERROR: 42P01: relation "nothing" does not exist
CONTEXT: PL/pgSQL function do_it(text) line 6 at RAISE