[Mailman-Users] wrapper returning '6' ... what does this mean?

I am trying to use exim with mailman. I've followed the directions at
http://mail.python.org/pipermail/mailman-users/2002-November/ 024041.html , but changing MAILMAN_WRAP=/usr/local/mailman/mail/wrapper
to MAILMAN_WRAP=/var/mailman/mail/mailman and changing the various
instances of config.db to config.pck.

When mail is passed to mailman, I get the following in my
/var/spool/exim/log/mainlog:

2003-09-15 23:40:19 19z2x8-0005cR-Ub ** thingies@3e.org
thingies-request@3e.org R=list_request_router
T=list_request_transport: Child process of list_request_transport
transport returned 6 from command: /var/mailman/mail/mailman

What does the return value '6' mean?

Daniel Drucker