# add-apt-repository cloud-archive:mitaka-proposed
# pwd
/etc/apt/sources.list.d

# cat cloudarchive-mitaka-proposed.list
deb http://ubuntu-cloud.archive.canonical.com/ubuntu trusty-proposed/mitaka main
# deb-src http://ubuntu-cloud.archive.canonical.com/ubuntu trusty-proposed/mitaka main

http://ubuntu-cloud.archive.canonical.com/ubuntu/dists/trusty-proposed/liberty/