no error if try to deploy to a container on a machine that does not exist

If you try to deploy to a container on a machine that does not exist, there is no error. Nor does the machine ever deploy.

If you add a unit to a container on a machine that does not exist, you get an error. Interestingly the unit is created, just has no machine.

If you try to deploy to a machine that does not exist, you get an error.

$ juju add-unit h --to lxd:4
ERROR acquiring machine to host unit "h/1": machine 4 not found (not found)
$ juju deploy ubuntu diffubuntu --to 4
Located charm "cs:ubuntu-15".
Deploying charm "cs:ubuntu-15".
ERROR cannot deploy "diffubuntu" to machine 4: machine 4 not found
$ juju deploy ubuntu --to lxd:4
Located charm "cs:ubuntu-15".
Deploying charm "cs:ubuntu-15".
$ juju status
Model Controller Cloud/Region Version SLA Timestamp
default maas-test localmaas/default 2.8.1.1 unsupported 18:34:31Z

App Version Status Scale Charm Store Rev OS Notes
h 18.04 waiting 1/2 lxd-profile-alt local 0 ubuntu
ubuntu waiting 0/1 ubuntu jujucharms 15 ubuntu

Unit Workload Agent Machine Public address Ports Message
h/0* active idle 0/lxd/0 172.16.99.34 ready
h/1 waiting allocating waiting for machine
ubuntu/0 waiting allocating waiting for machine

Machine State DNS Inst id Series AZ Message
0 started 172.16.99.33 huge-spider bionic default Deployed
0/lxd/0 started 172.16.99.34 juju-d04ab8-0-lxd-0 bionic default Container started