Comment 5 for bug 1747714

Verification done for xenial (nplan 0.32~16.04.4):

I used a dummy service on a new 16.04 install to have snap.network-manager.networkmanager.service available on the system.

dummy service:
[Unit]
Description=Test
DefaultDependencies=no
Conflicts=shutdown.target
Before=shutdown.target

[Service]
Type=oneshot
ExecStart=/usr/bin/logger -t toto test starting
ExecStop=/usr/bin/logger -t toto test stopping

[Install]
WantedBy=sysinit.target

netplan config:
network:
    version: 2
    renderer: NetworkManager
    ethernets:
        veth0:
            addresses:
                - 10.10.10.1/22

root@pleasing-koala:/etc/netplan# sudo netplan apply
Failed to start NetworkManager.service: Unit NetworkManager.service not found.
Traceback (most recent call last):
  File "/usr/sbin/netplan", line 418, in <module>
    eval('command_' + args.command.replace('-', '_'))()
  File "/usr/sbin/netplan", line 345, in command_apply
    systemctl_network_manager('start')
  File "/usr/sbin/netplan", line 104, in systemctl_network_manager
    subprocess.check_call(['systemctl', action, '--no-block', service_name])
  File "/usr/lib/python3.5/subprocess.py", line 581, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['systemctl', 'start', '--no-block', 'NetworkManager.service']' returned non-zero exit status 5
root@pleasing-koala:/etc/netplan# sudo systemctl enable snap.network-manager.networkmanager.service
Created symlink from /etc/systemd/system/sysinit.target.wants/snap.network-manager.networkmanager.service to /etc/systemd/system/snap.network-manager.networkmanager.service.
root@pleasing-koala:/etc/netplan# sudo netplan apply
root@pleasing-koala:/etc/netplan# sudo systemctl status snap.network-manager.networkmanager.service
● snap.network-manager.networkmanager.service - Test
   Loaded: loaded (/etc/systemd/system/snap.network-manager.networkmanager.service; enabled; vendor preset: enabled)
   Active: inactive (dead) since Mon 2018-03-19 15:42:09 UTC; 5s ago
  Process: 1190 ExecStop=/usr/bin/logger -t toto test stopping (code=exited, status=0/SUCCESS)
  Process: 1189 ExecStart=/usr/bin/logger -t toto test starting (code=exited, status=0/SUCCESS)
 Main PID: 1189 (code=exited, status=0/SUCCESS)

Mar 19 15:42:09 pleasing-koala systemd[1]: Starting Test...
Mar 19 15:42:09 pleasing-koala toto[1189]: test starting
Mar 19 15:42:09 pleasing-koala systemd[1]: Started Test.