Keystone uses PKI tokens by default, but they are very long and make the logs harder to read. Use the shorter UUID tokens instead:
KEYSTONE_TOKEN_FORMAT=UUID
To log to /opt/stack/logs/screen/
SCREEN_LOGDIR=$DEST/logs/screen
LOG_COLOR=false
LOGDAYS=4
LIBVIRT_TYPE=lxc
GIT_BASE="https://review.openstack.org/"