import_boot_images fails after upgrade from 1.5+bzr2252-0ubuntu1~ctools0 to 1.5.2+bzr2282-0ubuntu0.2

Previous install: precise + cloud-tools + cloud-tools-next + cloudarchive precise-updates/havana
Upgrade to: trusty, without any extra apt sources as above

Click on Clusters->"Import boot images" in the Web UI.

[2014-07-14 14:31:50,538: INFO/MainProcess] Received task: provisioningserver.tasks.import_boot_images[32dea5d7-45d4-45d0-ad09-f33ed14635f4]
[2014-07-14 14:31:50,551: ERROR/Worker-6] import_boot_images: Command `sudo -n -E maas-import-pxe-files` returned non-zero exit status 1:
None
[2014-07-14 14:31:50,589: ERROR/MainProcess] Task provisioningserver.tasks.import_boot_images[32dea5d7-45d4-45d0-ad09-f33ed14635f4] raised unexpected: ExternalProcessError()
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/celery/app/trace.py", line 218, in trace_task
    R = retval = fun(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/celery/app/trace.py", line 398, in __protected_call__
    return self.run(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/provisioningserver/tasks.py", line 95, in wrapper
    func(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/provisioningserver/tasks.py", line 464, in import_boot_images
    call_and_check(['sudo', '-n', '-E', 'maas-import-pxe-files'], env=env)
  File "/usr/lib/python2.7/dist-packages/provisioningserver/utils/__init__.py", line 121, in call_and_check
    return subprocess.check_call(command, *args, **kwargs)
  File "/usr/lib/python2.7/subprocess.py", line 540, in check_call
    raise CalledProcessError(retcode, cmd)
ExternalProcessError

ii maas 1.5.2+bzr2282-0ubuntu0.2 all MAAS server all-in-one metapackage
ii maas-cli 1.5.2+bzr2282-0ubuntu0.2 all MAAS command line API tool
ii maas-cluster-controller 1.5.2+bzr2282-0ubuntu0.2 all MAAS server cluster controller
ii maas-common 1.5.2+bzr2282-0ubuntu0.2 all MAAS server common files
ii maas-dhcp 1.5.2+bzr2282-0ubuntu0.2 all MAAS DHCP server
ii maas-dns 1.5.2+bzr2282-0ubuntu0.2 all MAAS DNS server
ii maas-region-controller 1.5.2+bzr2282-0ubuntu0.2 all MAAS server complete region controller
ii maas-region-controller-min 1.5.2+bzr2282-0ubuntu0.2 all MAAS Server minimum region controller
ii python-django-maas 1.5.2+bzr2282-0ubuntu0.2 all MAAS server Django web framework
ii python-maas-client 1.5.2+bzr2282-0ubuntu0.2 all MAAS python API client
ii python-maas-provisioningserver 1.5.2+bzr2282-0ubuntu0.2 all MAAS server provisioning libraries

Note: I cannot find any entry in /etc/sudoers for maas

Manually running maas-import-pxe-files as root succeeds.

/var/log/maas not included as it's 29MB tar.gz - please advise on how and where to ship logs if required.