To get more information about the problem when running test, use
assertIsInstance() function.

To simplify the login/logout, assemble all the handling of form
authentication into a single cherry tool. 
This new tools support the following feature:
- handle the session
- validate credential
- show login form when not login
- redirect to original page
- setup the `cherrypy.serving.request.login` with user object

Make testcases run in py2 and py3

translation too.