code: def process_post(self):
          
          if not self.check_lt():
              self.init_form(self.request.POST)
              logger.warning("Received an invalid login ticket")
              return self.INVALID_LOGIN_TICKET
          elif not self.request.session.get("authenticated") or self.renew:
              # authentication request receive, initialize the form to use
              self.init_form(self.request.POST)
              if self.form.is_valid():
                  self.request.session.set_expiry(0)
                  self.request.session["username"] = self.form.cleaned_data['username']
                  self.request.session["warn"] = True if self.form.cleaned_data.get("warn") else False
                  self.request.session["authenticated"] = True
                  self.renewed = True
                  self.warned = True
                  logger.info("User %s successfully authenticated" % self.request.session["username"])
                  return self.USER_LOGIN_OK
              else:
                  logger.warning("A login attempt failed")
                  return self.USER_LOGIN_FAILURE
          else:
              logger.warning("Received a login attempt for an already-active user")
              return self.USER_ALREADY_LOGGED
docs: Analyse the POST request:
  
                  * check that the LoginTicket is valid
                  * check that the user sumited credentials are valid
  
              :return:
                  * :attr:`INVALID_LOGIN_TICKET` if the POSTed LoginTicket is not valid
                  * :attr:`USER_ALREADY_LOGGED` if the user is already logged and do no request
                    reauthentication.
                  * :attr:`USER_LOGIN_FAILURE` if the user is not logged or request for
                    reauthentication and his credentials are not valid
                  * :attr:`USER_LOGIN_OK` if the user is not logged or request for
                    reauthentication and his credentials are valid
              :rtype: int