logging out while in project view creates an internal server error

steps to reproduce:

* be logged in to sloecode
* go to a project view (e. g. http://example.org/p/myproject42/index)
* hit the logout button
* BANG!

Content in /var/log/apache2/sloecode.error.log:

[Wed Jan 11 14:07:23 2012] [error] [client 156.62.70.135] [error] [client 156.62.70.135] Error - <type 'exceptions.KeyError'>: 'repoze.who.identity'

 Content in /var/apache2/sloecode.log:

156.62.70.135 - - [11/Jan/2012:14:07:23 +1300] "GET /sc/p/dms717287/index HTTP/1.1" 500 1072
156.62.70.135 - - [11/Jan/2012:14:07:23 +1300] "GET /sc/error/style/black.css HTTP/1.1" 404 1352

Stack trace by mail:

Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
Content-Type: text/plain; charset="UTF-8"

URL: http://putake.aut.ac.nz/sc/p/dms717287/index
File '/usr/lib/pymodules/python2.6/weberror/errormiddleware.py', line 162 in __call__
  app_iter = self.application(environ, sr_checker)
File '/usr/lib/pymodules/python2.6/repoze/who/middleware.py', line 107 in __call__
  app_iter = app(environ, wrapper.wrap_start_response)
File '/usr/lib/pymodules/python2.6/beaker/middleware.py', line 152 in __call__
  return self.wrap_app(environ, session_start_response)
File '/usr/lib/pymodules/python2.6/routes/middleware.py', line 131 in __call__
  response = self.app(environ, start_response)
File '/usr/lib/pymodules/python2.6/pylons/wsgiapp.py', line 124 in __call__
  response = self.dispatch(controller, environ, start_response)
File '/usr/lib/pymodules/python2.6/pylons/wsgiapp.py', line 327 in dispatch
  return controller(environ, start_response)
File '/usr/lib/python2.6/dist-packages/sloecode/lib/base.py', line 22 in __call__
  return WSGIController.__call__(self, environ, start_response)
File '/usr/lib/pymodules/python2.6/pylons/controllers/core.py', line 225 in __call__
  response = self._dispatch_call()
File '/usr/lib/pymodules/python2.6/pylons/controllers/core.py', line 176 in _dispatch_call
  response = self._inspect_call(func)
File '/usr/lib/pymodules/python2.6/pylons/controllers/core.py', line 108 in _inspect_call
  result = self._perform_call(func, args)
File '/usr/lib/pymodules/python2.6/pylons/controllers/core.py', line 60 in _perform_call
  return func(**args)
File '/usr/lib/python2.6/dist-packages/sloecode/controllers/project.py', line 37 in index
  user = request.environ['repoze.who.identity'].get('user')
KeyError: 'repoze.who.identity'

CGI Variables
-------------
  DOCUMENT_ROOT: '/var/www'
  GATEWAY_INTERFACE: 'CGI/1.1'
  HTTP_ACCEPT: 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8'
  HTTP_ACCEPT_CHARSET: 'ISO-8859-15,utf-8;q=0.7,*;q=0.7'
  HTTP_ACCEPT_LANGUAGE: 'en-nz,en;q=0.7,en-us;q=0.3'
  HTTP_CONNECTION: 'Keep-Alive'
  HTTP_COOKIE: 'sloecode=bc9df3aa97ec271598cd83e1336e76612acf9bfb9e00dba6341a5d8ebe7f006f687b09c8; __utma=95478083.824699417.1280966703.1288654595.1288658055.10'
  HTTP_DNT: '1'
  HTTP_HOST: 'putake.aut.ac.nz'
  HTTP_REFERER: 'http://putake.aut.ac.nz/sc/p/dms717287/index'
  HTTP_USER_AGENT: 'Mozilla/5.0 (Ubuntu; X11; Linux x86_64; rv:9.0.1) Gecko/20100101 Firefox/9.0.1'
  HTTP_X_FORWARDED_FOR: '156.62.70.135'
  HTTP_X_FORWARDED_HOST: 'putake.aut.ac.nz'
  HTTP_X_FORWARDED_SERVER: 'putake.aut.ac.nz'
  PATH_INFO: '/p/dms717287/index'
  PATH_TRANSLATED: '/var/www/p/dms717287/index'
  REMOTE_ADDR: '156.62.70.135'
  REMOTE_PORT: '60919'
  REQUEST_METHOD: 'GET'
  REQUEST_URI: '/sc/p/dms717287/index'
  SCRIPT_FILENAME: '/usr/share/sloecode/wsgi/sloecode.wsgi'
  SCRIPT_NAME: '/sc'
  SERVER_ADDR: '127.0.0.1'
  SERVER_ADMIN: '<email address hidden>'
  SERVER_NAME: 'putake.aut.ac.nz'
  SERVER_PORT: '8001'
  SERVER_PROTOCOL: 'HTTP/1.1'
  SERVER_SIGNATURE: '<address>Apache/2.2.16 (Debian) Server at putake.aut.ac.nz Port 8001</address>\n'
  SERVER_SOFTWARE: 'Apache/2.2.16 (Debian)'

WSGI Variables
--------------
  application: <repoze.who.middleware.PluggableAuthenticationMiddleware object at 0xba282d0c>
  beaker.get_session: <bound method SessionMiddleware._get_session of <beaker.middleware.SessionMiddleware object at 0xb9f79b4c>>
  beaker.session: {'_accessed_time': 1326244037.5890861, '_creation_time': 1326066463.573936}
  mod_wsgi.application_group: 'putake.aut.ac.nz:8001|/sc'
  mod_wsgi.callable_object: 'application'
  mod_wsgi.handler_script: ''
  mod_wsgi.input_chunked: '0'
  mod_wsgi.listener_host: ''
  mod_wsgi.listener_port: '8001'
  mod_wsgi.process_group: 'SloecodeWsgiDaemon'
  mod_wsgi.request_handler: 'wsgi-script'
  mod_wsgi.script_reloading: '1'
  mod_wsgi.version: (3, 3)
  paste.cookies: (<SimpleCookie: __utma='95478083.824699417.1280966703.1288654595.1288658055.10' sloecode='bc9df3aa97ec271598cd83e1336e76612acf9bfb9e00dba6341a5d8ebe7f006f687b09c8'>, 'sloecode=bc9df3aa97ec271598cd83e1336e76612acf9bfb9e00dba6341a5d8ebe7f006f687b09c8; __utma=95478083.824699417.1280966703.1288654595.1288658055.10')
  paste.registry: <paste.registry.Registry object at 0xbb5c730c>
  paste.throw_errors: True
  pylons.action_method: <bound method ProjectController.index of <sloecode.controllers.project.ProjectController object at 0xbb5dfd6c>>
  pylons.controller: <sloecode.controllers.project.ProjectController object at 0xbb5dfd6c>
  pylons.environ_config: {'session': 'beaker.session', 'cache': 'beaker.cache'}
  pylons.pylons: <pylons.util.PylonsContext object at 0xbb5dfa8c>
  pylons.routes_dict: {'action': u'index', 'controller': u'project', 'project_name': u'dms717287'}
  repoze.who.logger: None
  repoze.who.plugins: {'sa_md': <repoze.who.plugins.sa.SQLAlchemyUserMDPlugin object at 0xba278f4c>, 'sa_auth': <repoze.who.plugins.sa.SQLAlchemyAuthenticatorPlugin object at 0xb9fe524c>, 'auth_tkt': <AuthTktCookiePlugin 3123195660>, 'form': <FriendlyFormPlugin 3123193868>, 'authorization_md': <repoze.what.middleware.AuthorizationMetadata object at 0xba282bec>}
  routes.route: <routes.route.Route object at 0xb9f6f5cc>
  routes.url: <routes.util.URLGenerator object at 0xbb5c760c>
  webob.adhoc_attrs: {'language': 'en-us'}
  wsgi process: 'Multithreaded'
  wsgi.file_wrapper: <built-in method file_wrapper of mod_wsgi.Adapter object at 0xbb4be0f8>
  wsgi.version: (1, 1)
  wsgiorg.routing_args: (<routes.util.URLGenerator object at 0xbb5c760c>, {'action': u'index', 'controller': u'project', 'project_name': u'dms717287'})