mailman.client hangs accessing moderation queue

Here's what I did as recorded in Terminal.app:

steve@turnbull:~/src/Mailman3/mailman.client$ python
Python 2.7.3rc2 (default, Apr 22 2012, 22:30:17)
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> import time
>>> import subprocess
>>> from mailman.client import Client
>>> c = Client('http://localhost:8001/3.0', 'restadmin', 'restpass')
>>> dump(c.system)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'dump' is not defined
>>> c.lists
[<List "<email address hidden>">]
>>> c.domains
[<Domain "turnbull.sk.tsukuba.ac.jp">]
>>> print c.domains[0].url_host
turnbull.sk.tsukuba.ac.jp
>>> print c.domains[0].mail_host
turnbull.sk.tsukuba.ac.jp
>>> l = c.lists[0]
>>> l.fqdn_listname
<email address hidden>'
>>> c.get_list('<email address hidden>')
<List "<email address hidden>">
>>> c.get_list(<email address hidden>')
<List "<email address hidden>">
>>> c.members
[<Member "<email address hidden>" on "<email address hidden>">]
>>> print c.members[0].self_link
http://localhost:8001/3.0/members/230487102891977069915270988864921324936
>>> print c.members[0].link
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: '_Member' object has no attribute 'link'
>>> print c.users[0]
<User "None" (323817100493882819169277267745120573853)>
>>> print c.users
[<User "None" (323817100493882819169277267745120573853)>]
>>> print c.users[0].addresses
<mailman.client._client._Addresses object at 0x7f6b849c7a10>
>>> print c.users[0].addresses[0]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: '_Addresses' object does not support indexing
>>> for a in print c.users[0].addresses:
  File "<stdin>", line 1
    for a in print c.users[0].addresses:
                 ^
SyntaxError: invalid syntax
>>> for a in c.users[0].addresses:
... print a
...
<email address hidden>
>>> for a in sorted(l.settings):
... print a + ': ' + string(l.settings[a])
...
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
NameError: name 'string' is not defined
>>> for a in sorted(l.settings):
... print a + ': ' + str(l.settings[a])
...
acceptable_aliases: []
admin_immed_notify: True
admin_notify_mchanges: False
administrivia: True
advertised: True
allow_list_posts: True
anonymous_list: False
autorespond_owner: none
autorespond_postings: none
autorespond_requests: none
autoresponse_grace_period: 90d
autoresponse_owner_text:
autoresponse_postings_text:
autoresponse_request_text:
bounces_address: <email address hidden>
collapse_alternatives: True
convert_html_to_plaintext: False
created_at: 2012-08-09T03:16:21.186456
default_member_action: defer
default_nonmember_action: hold
description:
digest_last_sent_at: None
digest_size_threshold: 30.0
display_name: Mm3-test
filter_content: False
fqdn_listname: <email address hidden>
generic_nonmember_action: 1
http_etag: "b8b4e1df6bc8d8ee33f363927022d0bcc86569bb"
include_rfc2369_headers: True
join_address: <email address hidden>
last_post_at: None
leave_address: <email address hidden>
list_name: mm3-test
mail_host: turnbull.sk.tsukuba.ac.jp
next_digest_number: 1
no_reply_address: <email address hidden>
owner_address: <email address hidden>
post_id: 1
posting_address: <email address hidden>
posting_pipeline: default-posting-pipeline
reply_goes_to_list: no_munging
request_address: <email address hidden>
scheme: http
send_welcome_message: True
volume: 1
web_host: turnbull.sk.tsukuba.ac.jp
welcome_message_uri: mailman:///welcome.txt
>>> dir()
['Client', '__builtins__', '__doc__', '__name__', '__package__', 'a', 'c', 'l', 'os', 'subprocess', 'time']
>>> dir(Client)
['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'create_domain', 'delete_domain', 'delete_list', 'domains', 'get_domain', 'get_list', 'get_user', 'lists', 'members', 'preferences', 'system', 'users']
>>> dir(Client.system)
['__class__', '__delattr__', '__delete__', '__doc__', '__format__', '__get__', '__getattribute__', '__hash__', '__init__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__set__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'deleter', 'fdel', 'fget', 'fset', 'getter', 'setter']
>>> dir(l)
['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', '_connection', '_get_info', '_info', '_url', 'accept_message', 'defer_message', 'delete', 'discard_message', 'display_name', 'fqdn_listname', 'get_member', 'held', 'list_name', 'mail_host', 'members', 'moderate_message', 'reject_message', 'settings', 'subscribe', 'unsubscribe']
>>> l._connection.__doc__
u'A connection to the REST client.'
>>> l.held.__doc__

^CTraceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "mailman/client/_client.py", line 350, in held
    'lists/{0}/held'.format(self.fqdn_listname), None, 'GET')
  File "mailman/client/_client.py", line 114, in call
    response, content = Http().request(url, method, data, headers)
  File "/usr/lib/python2.7/dist-packages/httplib2/__init__.py", line 1543, in request
    (response, content) = self._request(conn, authority, uri, request_uri, method, body, headers, redirections, cachekey)
  File "/usr/lib/python2.7/dist-packages/httplib2/__init__.py", line 1293, in _request
    (response, content) = self._conn_request(conn, request_uri, method, body, headers)
  File "/usr/lib/python2.7/dist-packages/httplib2/__init__.py", line 1263, in _conn_request
    response = conn.getresponse()
  File "/usr/lib/python2.7/httplib.py", line 1030, in getresponse
    response.begin()
  File "/usr/lib/python2.7/httplib.py", line 407, in begin
    version, status, reason = self._read_status()
  File "/usr/lib/python2.7/httplib.py", line 365, in _read_status
    line = self.fp.readline()
  File "/usr/lib/python2.7/socket.py", line 430, in readline
    data = recv(1)
  File "/home/steve/src/Mailman3/mailman-trunk/src/mailman/email/message.py", l\
ine 226, in _enqueue
    virginq.enqueue(self, **str_keywords)
  File "/home/steve/src/Mailman3/mailman-trunk/src/mailman/core/switchboard.py"\
, line 123, in enqueue
    msgsave = cPickle.dumps(_msg, protocol)

After the above I tried a couple of things, like printing l.held (with no further attribute). These also hung for a few seconds and I interrupted with ^C.

Eventually it failed with an error about not being connected to Mailman. I thought Mailman had crashed, but when I tried shutting down Mailman using bin/mailman, it seemed to shut down normally.