TypeError: load() missing 1 required positional argument: 'Loader'

I'm seeing failures deploying lunar to an arm64 server, curtin 2.1-0ubuntu1~22.04.1, MAAS 3.3:

       Running command ['unshare', '--help'] with allowed return codes [0] (capture=True)
        Running command ['unshare', '--fork', '--pid', '--', 'chroot', '/tmp/tmp6un94l9v/target', 'lsb_release', '--all'] with allowed return codes [0] (capture=True)
        Running command ['unshare', '--fork', '--pid', '--', 'chroot', '/tmp/tmp6un94l9v/target', 'dpkg', '--print-architecture'] with allowed return codes [0] (capture=True)
        got primary mirror: None
        got security mirror: None
        Apt Mirror info: {'PRIMARY': 'http://ports.ubuntu.com/ubuntu-ports', 'SECURITY': 'http://ports.ubuntu.com/ubuntu-ports', 'MIRROR': 'http://ports.ubuntu.com/ubuntu-ports'}
        Applying debconf selections
        Running command ['unshare', '--fork', '--pid', '--', 'chroot', '/tmp/tmp6un94l9v/target', 'debconf-set-selections'] with allowed return codes [0] (capture=True)
        Running command ['unshare', '--fork', '--pid', '--', 'chroot', '/tmp/tmp6un94l9v/target', 'dpkg-query', '--list'] with allowed return codes [0] (capture=True)
        unconfiguring cloud-init
        cleaning cloud-init config from: ['/tmp/tmp6un94l9v/target/etc/cloud/cloud.cfg.d/90_dpkg.cfg']
        Running command ['unshare', '--fork', '--pid', '--', 'chroot', '/tmp/tmp6un94l9v/target', 'dpkg-reconfigure', '--frontend=noninteractive', 'cloud-init'] with allowed return codes [0] (capture=True)
        finish: cmd-install/stage-curthooks/builtin/cmd-curthooks/writing-apt-config: FAIL: configuring apt configuring apt
        finish: cmd-install/stage-curthooks/builtin/cmd-curthooks: FAIL: curtin command curthooks
        Traceback (most recent call last):
          File "/curtin/curtin/commands/main.py", line 202, in main
            ret = args.func(args)
                  ^^^^^^^^^^^^^^^
          File "/curtin/curtin/commands/curthooks.py", line 1886, in curthooks
            builtin_curthooks(cfg, target, state)
          File "/curtin/curtin/commands/curthooks.py", line 1692, in builtin_curthooks
            do_apt_config(cfg, target)
          File "/curtin/curtin/commands/curthooks.py", line 97, in do_apt_config
            apt_config.handle_apt(apt_cfg, target)
          File "/curtin/curtin/commands/apt_config.py", line 73, in handle_apt
            apply_debconf_selections(cfg, target)
          File "/curtin/curtin/commands/apt_config.py", line 167, in apply_debconf_selections
            dpkg_reconfigure(need_reconfig, target=target)
          File "/curtin/curtin/commands/apt_config.py", line 133, in dpkg_reconfigure
            util.subp(['dpkg-reconfigure', '--frontend=noninteractive'] +
          File "/curtin/curtin/util.py", line 275, in subp
            return _subp(*args, **kwargs)
                   ^^^^^^^^^^^^^^^^^^^^^^
          File "/curtin/curtin/util.py", line 139, in _subp
            raise ProcessExecutionError(stdout=out, stderr=err,
        curtin.util.ProcessExecutionError: Unexpected error while running command.
        Command: ['unshare', '--fork', '--pid', '--', 'chroot', '/tmp/tmp6un94l9v/target', 'dpkg-reconfigure', '--frontend=noninteractive', 'cloud-init']
        Exit code: 1
        Reason: -
        Stdout: ''
        Stderr: Traceback (most recent call last):
                  File "<string>", line 23, in <module>
                TypeError: load() missing 1 required positional argument: 'Loader'

        Unexpected error while running command.
        Command: ['unshare', '--fork', '--pid', '--', 'chroot', '/tmp/tmp6un94l9v/target', 'dpkg-reconfigure', '--frontend=noninteractive', 'cloud-init']
        Exit code: 1
        Reason: -
        Stdout: ''
        Stderr: Traceback (most recent call last):
                  File "<string>", line 23, in <module>
                TypeError: load() missing 1 required positional argument: 'Loader'

Stderr: ''