Object has no comparison on login.html

We're getting a couple of these a day:

TypeError: Object has default comparison
Exception when processing https://karl.soros.org/login.html
Referer: https://karl.soros.org/login.html

Traceback (most recent call last):
  File "/srv/osfkarl/production/89/eggs/pyramid-1.2.1-py2.7.egg/pyramid/tweens.py", line 17, in excview_tween
    response = handler(request)
  File "/srv/osfkarl/production/89/eggs/pyramid_tm-0.5-py2.7.egg/pyramid_tm/__init__.py", line 107, in tm_tween
    return response
  File "/srv/osfkarl/production/89/eggs/pyramid_tm-0.5-py2.7.egg/pyramid_tm/__init__.py", line 75, in __exit__
    return self._retry_or_raise(t, v, tb)
  File "/srv/osfkarl/production/89/eggs/pyramid_tm-0.5-py2.7.egg/pyramid_tm/__init__.py", line 60, in _retry_or_raise
    reraise(t, v, tb) # otherwise reraise the exception
  File "/srv/osfkarl/production/89/eggs/pyramid_tm-0.5-py2.7.egg/pyramid_tm/__init__.py", line 100, in tm_tween
    response = handler(request)
  File "/srv/osfkarl/production/89/eggs/pyramid-1.2.1-py2.7.egg/pyramid/router.py", line 153, in handle_request
    response = view_callable(context, request)
  File "/srv/osfkarl/production/89/eggs/pyramid-1.2.1-py2.7.egg/pyramid/config/views.py", line 319, in viewresult_to_response
    result = view(context, request)
  File "/srv/osfkarl/production/89/eggs/karl-4.23.2-py2.7.egg/karl/views/login.py", line 141, in login_view
    userid = _authenticate(context, login, password)
  File "/srv/osfkarl/production/89/eggs/karl-4.23.2-py2.7.egg/karl/views/login.py", line 68, in _authenticate
    userid = authenticate(users, login, password)
  File "/srv/osfkarl/production/89/eggs/karl-4.23.2-py2.7.egg/karl/views/login.py", line 287, in password_authenticator
    user = users.get(login=login)
  File "/srv/osfkarl/production/89/eggs/repoze.whoplugins.zodb-1.0.1-py2.7.egg/repoze/who/plugins/zodb/users.py", line 78, in get
    return self.data.get(userid)
TypeError: Object has default comparison