Cannot access localhost:8000 (Postorius error)

I just got to setup postorius along with mailman 3, in two separate virtual environments using Python2 and Python3 respectively. I also deleted the Middleware import of postorius.middleware.PostoriusMiddleware because that module was not found. Now I am running "python manage.py runserver" and then getting this error:

The console shows the following error message:

Performing system checks...

System check identified no issues (0 silenced).
March 29, 2016 - 10:09:35
Django version 1.8.11, using settings 'settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.
django_browserid using default Verify view.
Internal Server Error: /
Traceback (most recent call last):
  File "/tmp/postorius/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 132, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/tmp/postorius/local/lib/python2.7/site-packages/postorius/views/list.py", line 511, in list_index
    lists = sorted(List.objects.all(only_public=only_public),
  File "/tmp/postorius/local/lib/python2.7/site-packages/postorius/models.py", line 144, in all
    objects = getattr(get_client(), self.resource_name_plural)
  File "/tmp/postorius/local/lib/python2.7/site-packages/mailmanclient/_client.py", line 158, in lists
    response, content = self._connection.call('lists')
  File "/tmp/postorius/local/lib/python2.7/site-packages/mailmanclient/_client.py", line 109, in call
    raise HTTPError(url, response.status, content, response, None)
HTTPError: HTTP Error 500: A server error occurred.  Please contact the administrator.
[29/Mar/2016 10:09:38] "GET / HTTP/1.1" 500 89727

My mailman core in the python3 virtual environment shows this error:

File "/usr/lib/python3.4/wsgiref/handlers.py", line 137, in run
    self.result = application(self.environ, self.start_response)
  File "/home/rohit/Downloads/mailman-3.0.0/src/mailman/database/transaction.py", line 57, in wrapper
    rtn = function(*args, **kws)
  File "/home/rohit/Downloads/mailman-3.0.0/src/mailman/rest/wsgiapp.py", line 65, in __call__
    environ, start_response)
  File "/tmp/mailman3/lib/python3.4/site-packages/falcon-1.0.0rc1-py3.4.egg/falcon/api.py", line 175, in __call__
    responder, params, resource = self._get_responder(req)
  File "/home/rohit/Downloads/mailman-3.0.0/src/mailman/rest/wsgiapp.py", line 135, in _get_responder
    method_map = create_http_method_map(resource, None, None)
TypeError: create_http_method_map() takes 1 positional argument but 3 were given

Can anybody help me out with this?