debootstrap fails for trisquel benelos repo

sudo pbuilder create --debootstrapopts --variant=buildd --distribution belenos
I: Distribution is belenos.
I: Current time: Sat Nov 29 18:09:31 CET 2014
I: pbuilder-time-stamp: 1417280971
I: Building the build environment
I: running debootstrap
/usr/sbin/debootstrap
I: Retrieving Release
I: Retrieving Release.gpg
I: Checking Release signature
E: Release signed by unknown key (key id B4EFB9F38D8AEBF1)
E: debootstrap failed
W: Aborting with an error
I: cleaning the build env
I: removing directory /var/cache/pbuilder/build//15932 and its subdirectories

How do I import the public key for the release