'NetplanApply' object has no attribute 'state'

[Carlos F.]

No matter the netplan configuration, it always fails with 'NetplanApply' object has no attribute 'state'.

###
network:
    version: 2
    ethernets:
        eth0:
            addresses:
            - 2a01:5f9:a2c:d230::1/64
            dhcp4: true
            gateway6: fe80::1
            match:
                macaddress: 96:00:00:e4:cd:cb
            set-name: eth0

# netplan try
Warning: Stopping systemd-networkd.service, but it can still be activated by:
  systemd-networkd.socket

An error occurred: 'NetplanApply' object has no attribute 'state'

Reverting.
Warning: Stopping systemd-networkd.service, but it can still be activated by:
  systemd-networkd.socket

### Installed packages

libnetplan0/0.103-0ubuntu5~20.04.2 amd64
netplan.io/0.103-0ubuntu5~20.04.2 amd64

### No such problem on another machine with:

libnetplan0/0.103-0ubuntu5~20.04.1 amd64
netplan.io/0.103-0ubuntu5~20.04.1 amd64

[Carlos F. (acsfer)]

I can reproduce it on any machine just after upgrading from

###
libnetplan0/0.103-0ubuntu5~20.04.1 amd64
netplan.io/0.103-0ubuntu5~20.04.1 amd64

to

###
libnetplan0/0.103-0ubuntu5~20.04.2 amd64
netplan.io/0.103-0ubuntu5~20.04.2 amd64

Without any configuration changes; just 'apt upgrade' and run 'netplan try' afterwards.