make-live iso exits with cryptic message

[andrea at tasso.info (Andrea Tasso)]

thanks, it works, but there is another problem:

[...]
The following NEW packages will be installed:
casper squashfs-modules-2.6-486 squashfs-modules-2.6.16-2-486
unionfs-modules-2.6-486 unionfs-modules-2.6.16-2-486 user-setup
0 upgraded, 6 newly installed, 0 to remove and 0 not upgraded.
Need to get 289kB of archives.
After unpacking 1085kB of additional disk space will be used.
WARNING: The following packages cannot be authenticated!
unionfs-modules-2.6.16-2-486 unionfs-modules-2.6-486 casper
E: There are problems and -y was used without --force-yes


ciao

Andrea