error!

__init__.py

from pyramid.config import Configurator

from pyramid.authentication import AuthTktAuthenticationPolicy
from pyramid.authorization import ACLAuthorizationPolicy
from apogee.security import groupfinder

from sqlalchemy import engine_from_config

from .models import DBSession

def main(global_config, **settings):
    """ This function returns a Pyramid WSGI application.
    """
    engine = engine_from_config(settings, 'sqlalchemy.')
    DBSession.configure(bind=engine)

    """
    Authentication/Authorization
    """
    authn_policy = AuthTktAuthenticationPolicy(
        'sosecret', callback=groupfinder)
    authz_policy = ACLAuthorizationPolicy()

    """
    Config
    """
    config = Configurator(settings=settings,
					          root_factory='apogee.models.RootFactory',
					          authentication_policy=authn_policy,
					          authorization_policy=authz_policy)

    """
    Routes
    """
    config.add_static_view('static', 'static', cache_max_age=3600)
    config.add_route('view_wiki', '/')
    config.add_route('login', '/login')
    config.add_route('logout', '/logout')
    config.add_route('view_page', '/{pagename}')
    config.add_route('add_page', '/add_page/{pagename}')
    config.add_route('edit_page', '/{pagename}/edit_page')
    config.scan()
    return config.make_wsgi_app()

gistfile1.pytb

Traceback (most recent call last):
  File "c:\env\memeplace\pyramid_debugtoolbar-0.9.7-py2.7.egg\pyramid_debugtoolbar\panels\performance.py", line 69, in noresource_timer_handler
    result = handler(request)
  File "C:\env\lib\site-packages\pyramid-1.3a2-py2.7.egg\pyramid\tweens.py", line 20, in excview_tween
    response = handler(request)
  File "C:\env\lib\site-packages\pyramid_tm-0.3-py2.7.egg\pyramid_tm\__init__.py", line 61, in tm_tween
    response = handler(request)
  File "C:\env\lib\site-packages\pyramid-1.3a2-py2.7.egg\pyramid\router.py", line 164, in handle_request
    response = view_callable(context, request)
  File "C:\env\lib\site-packages\pyramid-1.3a2-py2.7.egg\pyramid\config\views.py", line 316, in rendered_view
    result = view(context, request)
  File "C:\env\lib\site-packages\pyramid-1.3a2-py2.7.egg\pyramid\config\views.py", line 426, in _requestonly_view
    response = view(request)
  File "c:\env\apogee\apogee\views.py", line 108, in login
    if USERS.get(login) == password:
NameError: global name 'USERS' is not defined

security.py

USERS = {'editor':'editor',
          'viewer':'viewer'}
GROUPS = {'editor':['group:editors']}

def groupfinder(userid, request):
    if userid in USERS:
        return GROUPS.get(userid, [])