def login(self, login=None, password=None):
        """ Login with default or supplied credetials.

        .. note::

            Calling this method is not necessary when HTTP basic or HTTP
            digest_auth authentication is used and RT accepts it as external
            authentication method, because the login in this case is done
            transparently by requests module. Anyway this method can be useful
            to check whether given credentials are valid or not.

        :keyword login: Username used for RT, if not supplied together with
                        *password* :py:attr:`~Rt.default_login` and
                        :py:attr:`~Rt.default_password` are used instead
        :keyword password: Similarly as *login*

        :returns: ``True``
                      Successful login
                  ``False``
                      Otherwise
        :raises AuthorizationError: In case that credentials are not supplied neither
                                    during inicialization or call of this method.
        """

        if (login is not None) and (password is not None):
            login_data = {'user': login, 'pass': password}
        elif (self.default_login is not None) and (self.default_password is not None):
            login_data = {'user': self.default_login, 'pass': self.default_password}
        elif self.session.auth:
            login_data = None
        else:
            raise AuthorizationError('Credentials required, fill login and password.')
        try:
            self.login_result = self.__get_status_code(self.__request('',
                                                                      post_data=login_data,
                                                                      without_login=True)) == 200
        except AuthorizationError:
            # This happens when HTTP Basic or Digest authentication fails, but
            # we will not raise the error but just return False to indicate
            # invalid credentials
            return False
        return self.login_result
Login with default or supplied credetials.

        .. note::

            Calling this method is not necessary when HTTP basic or HTTP
            digest_auth authentication is used and RT accepts it as external
            authentication method, because the login in this case is done
            transparently by requests module. Anyway this method can be useful
            to check whether given credentials are valid or not.

        :keyword login: Username used for RT, if not supplied together with
                        *password* :py:attr:`~Rt.default_login` and
                        :py:attr:`~Rt.default_password` are used instead
        :keyword password: Similarly as *login*

        :returns: ``True``
                      Successful login
                  ``False``
                      Otherwise
        :raises AuthorizationError: In case that credentials are not supplied neither
                                    during inicialization or call of this method.