Bareos, dbconfig-common, PostgreSQL and PAM: no module specific data

[Ralph Aichinger <ralph@pi.h5.or.at>]

(Sorry if this is a duplicate message, I tried to post this
an hour or so ago, but saw nothing on the list.)

I want to install bareos, the bacula derived backup software
with a PostgreSQL/dbconfig setup on a sid/amd64 system. I am
stuck at the following error:

An error occurred while installing the database:                         
  │                                                                        
  │ Password for user bareos: psql: FATAL: password authentication failed 
  │ for user "bareos" FATAL: password authentication failed for user  
  │ "bareos" su: No module specific data is present          

I assume the "No module specific data is present" refers to PAM modules?

Any hints on how to resolve that problem or diagnose it further?

TIA
/ralph