Tested on a Trusty 14.04.5 VM with updates installed, trusty-proposed pinned for selective upgrade.
$ sudo apt-get install snapd/trusty-proposed snap-confine/trusty-proposed xserver-xorg-core-lts-xenial/trusty-proposed
This installed the packages correctly, including systemd.
Tested on a Trusty 14.04.5 VM with updates installed, trusty-proposed pinned for selective upgrade.
$ sudo apt-get install snapd/trusty- proposed snap-confine/ trusty- proposed xserver- xorg-core- lts-xenial/ trusty- proposed
This installed the packages correctly, including systemd.