Hi,
The Vagrant basebox has been updated, and apparently Vagrant won't
switch to it automatically. To completely delete the old builder VM and
basebox, please run these commands from Tails' Git root:
rake vm:halt
rake vm:destroy
vagrant box remove tails-builder-amd64-jessie-20160226
VOLS="$(virsh vol-list default | \
grep -o "tails-builder-amd64-jessie-20160226\S*\.img" | \
uniq)"
for vol in ${VOLS}; do virsh vol-delete --pool default ${vol}; done
To get the new Vagrant basebox, make sure to checkout a recent `devel`
(or merge it into the branch you want to build), and then run `rake
build` or `rake vm:up` or whatever you prefer.
Cheers!