BUG #5583: dblink connection error

The following bug has been logged online:

Bug reference: 5583
Logged by: Piergiorgio Buongiovanni
Email address: piergiorgio(dot)buongiovanni(at)netspa(dot)it
PostgreSQL version: 8.4.3
Operating system: x86_64-redhat-linux-gnu
Description: dblink connection error
Details:

We are trying to use dblink and following instructions on your manual pages
we are trying to execute the following command with user sa on a db named
netdw:

SELECT * FROM dblink(
'dbname=lportal',
'SELECT b.name FROM users_roles a LEFT OUTER JOIN role_ b ON b.roleid =
a.roleid WHERE a.userid = 13902 ORDER BY 1')
AS roles (Role varchar)

The above command works and returns a list of roles as expected. If now we
change the user and execute the following command with user netdw_owner on
the same db named netdw:

SELECT * FROM dblink(
'dbname=lportal user=sa password=xxx',
'SELECT b.name FROM users_roles a LEFT OUTER JOIN role_ b ON b.roleid =
a.roleid WHERE a.userid = 13902 ORDER BY 1')
AS roles (Role varchar)

we obtain the following error:

ERROR: password is required
DETAIL: Non-superuser cannot connect if the server does not request a
password.
HINT: Target server's authentication method must be changed.

********** Errore **********

ERROR: password is required
Stato SQL: 2F003
Dettaglio: Non-superuser cannot connect if the server does not request a
password.
Suggerimento: Target server's authentication method must be changed.

Could you explain how to solve this problem?
Regards.