enable-ha can end up in an unsolvable state when there is an error during deployment

Scenario:
$ juju bootstrap maas
$ juju enable-ha -n 3 --to machine1,machine2

When it's already allocated but not yet deployed - kill machine1 in MAAS (it can also be later, then it won't be 'PENDING' but 'DOWN')

Wait for deployment on machine2 to finish, and then:

$ juju enable-ha -n 3 --to machine1

This will demote machine 1@machine1 (still in pending/down state) and add machine 3@machine1

After all the machines are deployed and HA cluster is working (machines 0,2,3 in 'ha-enabled' state) we've got the following situation:

Machine State DNS Inst id Series AZ Message
0 started 10.2.15.254 ct3y86 xenial default Deployed
1 pending 10.2.0.3 b73t3a xenial default Deploying: ubuntu/amd64/ga-16.04/xenial/daily/boot-initrd
2 started 10.2.0.4 tg34tr xenial default Deployed
3 started 10.2.0.3 b73t3a xenial default Deployed

With two Juju machines set up on one MAAS machine.

To clean up the HA state:
$ juju enable-ha -n 3
maintaining machines: 0, 2, 3
removing machines: 1

And now we can safely remove machine 1:
$ juju remove-machine 1 --force

According to juju everything is OK:
Machine State DNS Inst id Series AZ Message
0 started 10.2.15.254 ct3y86 xenial default Deployed
2 started 10.2.0.4 tg34tr xenial default Deployed
3 started 10.2.0.3 b73t3a xenial default Deployed

But the facts are that b73t3a was decomissioned by Juju from MAAS and it's really dead (juju doesn't notice it for quite some time - IMHO it should be more robust)

I haven't found a way to remove this pending/dead 'doppelganger' machine from machines list, maybe a '--no-action' switch to remove-machine would be needed?