[2.3] Unable to delete users with reserved IPs

MAAS Version 1.9.4+bzr4592-0ubuntu1 (trusty1)

Attempting to delete a user and get an ugly 500 Internal server error page after confirming.

Snippet from regiond.log ( https://pastebin.canonical.com/171089/ for formatting )

2016-11-18 10:15:38 [HTTPChannel,10748,127.0.0.1] 500 Error - /MAAS/accounts/tribaal/del/
        Traceback (most recent call last):
          File "/usr/lib/python2.7/dist-packages/django/core/handlers/wsgi.py", line 206, in __call__
            response = self.get_response(request)
          File "/usr/lib/python2.7/dist-packages/maasserver/utils/views.py", line 236, in get_response
            response = get_response(request)
          File "/usr/lib/python2.7/dist-packages/maasserver/utils/views.py", line 210, in get_response
            return django_get_response(request)
          File "/usr/lib/python2.7/dist-packages/django/core/handlers/base.py", line 194, in get_response
            response = self.handle_uncaught_exception(request, resolver, sys.exc_info())
        --- <exception caught here> ---
          File "/usr/lib/python2.7/dist-packages/django/core/handlers/base.py", line 112, in get_response
            response = wrapped_callback(request, *callback_args, **callback_kwargs)
          File "/usr/lib/python2.7/dist-packages/maasserver/utils/views.py", line 189, in view_atomic_with_post_commit_savepoint
            return view_atomic(*args, **kwargs)
          File "/usr/lib/python2.7/dist-packages/django/db/transaction.py", line 339, in inner
            return func(*args, **kwargs)
          File "/usr/lib/python2.7/dist-packages/django/contrib/auth/decorators.py", line 22, in _wrapped_view
            return view_func(request, *args, **kwargs)
          File "/usr/lib/python2.7/dist-packages/django/views/generic/base.py", line 69, in view
            return self.dispatch(request, *args, **kwargs)
          File "/usr/lib/python2.7/dist-packages/django/views/generic/base.py", line 87, in dispatch
            return handler(request, *args, **kwargs)
          File "/usr/lib/python2.7/dist-packages/django/views/generic/edit.py", line 257, in post
            return self.delete(request, *args, **kwargs)
          File "/usr/lib/python2.7/dist-packages/maasserver/views/settings.py", line 116, in delete
            profile.delete()
          File "/usr/lib/python2.7/dist-packages/maasserver/models/userprofile.py", line 82, in delete
            self.user.delete()
          File "/usr/lib/python2.7/dist-packages/django/db/models/base.py", line 694, in delete
            collector.collect([self])
          File "/usr/lib/python2.7/dist-packages/django/db/models/deletion.py", line 197, in collect
            field.rel.on_delete(self, field, sub_objs, self.using)
          File "/usr/lib/python2.7/dist-packages/django/db/models/deletion.py", line 27, in PROTECT
            sub_objs
        django.db.models.deletion.ProtectedError: ("Cannot delete some instances of model 'User' because they are referenced through a protected foreign key: 'StaticIPAddress.user'", [<StaticIPAddress: 10.1.100.1:type=USER_RESERVED>, <StaticIPAddress: 10.1.100.9:type=USER_RESERVED>, <StaticIPAddress: 10.1.100.13:type=USER_RESERVED>, <StaticIPAddress: 10.1.100.14:type=USER_RESERVED>, <StaticIPAddress: 10.1.100.15:type=USER_RESERVED>, <StaticIPAddress: 10.1.100.16:type=USER_RESERVED>, <StaticIPAddress: 10.1.100.17:type=USER_RESERVED>, <StaticIPAddress: 10.1.100.18:type=USER_RESERVED>, <StaticIPAddress: 10.1.100.19:type=USER_RESERVED>, <StaticIPAddress: 10.1.100.20:type=USER_RESERVED>, <StaticIPAddress: 10.1.100.3:type=USER_RESERVED>, <StaticIPAddress: 10.1.100.10:type=USER_RESERVED>, <StaticIPAddress: 10.1.100.4:type=USER_RESERVED>, <StaticIPAddress: 10.1.100.11:type=USER_RESERVED>, <StaticIPAddress: 10.1.100.5:type=USER_RESERVED>, <StaticIPAddress: 10.1.100.6:type=USER_RESERVED>, <StaticIPAddress: 10.1.100.7:type=USER_RESERVED>])