Invalid Null Namespace While Trying To Login

While trying to authenticate at openid-please, I'm getting the following error:

ValueError: Invalid null namespace: u'http://openid.net/signon/2.0'

The traceback provided by Python is:

Traceback (most recent call last):
File "/base/python_lib/versions/1/google/appengine/ext/webapp/__init__.py", line 499, in __call__
handler.get(*groups)
File "/base/data/home/apps/openid-please/1.9/please.py", line 317, in get
auth_response = self.get_consumer().complete(args, self.request.uri)
File "/base/data/home/apps/openid-please/1.9/openid/consumer/consumer.py", line 414, in complete
response = self.consumer.complete(message, endpoint, return_to)
File "/base/data/home/apps/openid-please/1.9/openid/consumer/consumer.py", line 619, in complete
return modeMethod(message, endpoint, return_to)
File "/base/data/home/apps/openid-please/1.9/openid/consumer/consumer.py", line 645, in _complete_id_res
return self._doIdRes(message, endpoint, return_to)
File "/base/data/home/apps/openid-please/1.9/openid/consumer/consumer.py", line 734, in _doIdRes
self._idResCheckSignature(message, endpoint.server_url)
File "/base/data/home/apps/openid-please/1.9/openid/consumer/consumer.py", line 802, in _idResCheckSignature
if not self._checkAuth(message, server_url):
File "/base/data/home/apps/openid-please/1.9/openid/consumer/consumer.py", line 1094, in _checkAuth
response = self._makeKVPost(request, server_url)
File "/base/data/home/apps/openid-please/1.9/openid/consumer/consumer.py", line 229, in makeKVPost
return _httpResponseToMessage(resp, server_url)
File "/base/data/home/apps/openid-please/1.9/openid/consumer/consumer.py", line 246, in _httpResponseToMessage
response_message = Message.fromKVForm(response.body)
File "/base/data/home/apps/openid-please/1.9/openid/message.py", line 225, in fromKVForm
return cls.fromOpenIDArgs(kvform.kvToDict(kvform_string))
File "/base/data/home/apps/openid-please/1.9/openid/message.py", line 154, in fromOpenIDArgs
self._fromOpenIDArgs(openid_args)
File "/base/data/home/apps/openid-please/1.9/openid/message.py", line 185, in _fromOpenIDArgs
self.setOpenIDNamespace(openid_ns_uri)
File "/base/data/home/apps/openid-please/1.9/openid/message.py", line 209, in setOpenIDNamespace
raise ValueError('Invalid null namespace: %r' % (openid_ns_uri,))

This is occurring at the following URL:

http://openid-please.appspot.com/open...

The OpenID I'm trying to use, if it isn't already obvious from the above, is:

https://tjohns.net

Any ideas?