'Process an error that occurs during command execution.
Arguments:
iq      -- The iq stanza containing the error.
session -- A dictionary of data relevant to the command
session. Additional, custom data may be saved
here to persist across handler callbacks.'

def _command_error(self, iq, session):

    logging.error(('COMMAND:    %s    %s' % (iq['error']['condition'], iq['error']['text'])))
    self['xep_0050'].terminate_command(session)
    self.disconnect()
