Updated authentify handler method to raises better exceptions.

        try:

            role = self._server.conf.authentify(login, password)

        except CCConf.UnknownAccount:

            raise AuthenticationError('Authentication failure (Unknown login)')

            raise AuthenticationError('Unknown login')

        if role is None:

            logging.info('New authentication from %s: failure' % login)

            raise AuthenticationError('Authentication failure')

            raise AuthenticationError('Bad login/password')

        else:

            # If authentication is a success, try to register the client:

            try:

                self._server.register(login, role, connection)

                self._server.register(login, role, conn)

            except AlreadyRegistered:

                raise AuthenticationError('Authentication failure '

                                          '(already connected)')

            connection.set_handler(WelcomeHandler.ROLES.get(role)(self._server))

            logging.info('New authentication from %s: success' % login)

                raise AuthenticationError('Already connected')

            conn.set_handler(WelcomeHandler.ROLES.get(role)(self._server))

            return role