[Mailman-Users] check_perms error?

[nikos]

Hello list

This is my first try in mailman.
I run mailman-2.1-8 in a RH9 Linux with python-2.2.2-26.
Mailman installed automaticaly from redhat installer.

When I run check_perms in /var/mailman/bin/ directory the following message
shows. Is that problem and how can I solve it before continuing

Traceback (most recent call last):
  File "./check_perms", line 51, in ?
    MAILMAN_GID = grp.getgrnam(MAILMAN_GROUP)[2]
KeyError: getgrnam(): name not found

I have run check_perms -f but i got the same error

Thank you