code: def get_box_id(logger):
      
      try:
          box_id = None
          config_file = settings.settings['config_file']
          with open(config_file) as a_file:
              for a_line in a_file:
                  a_line = a_line.strip()
                  if a_line.startswith('#'):
                      continue
  
                  tokens = a_line.split('=')
                  if tokens[0] == 'BOX_ID':
                      box_id = tokens[1]
                      return box_id
  
          if box_id is None:
              raise LookupError('BOX_ID is not defined in {0}'.format(config_file))
  
      except EnvironmentError:  # parent of IOError, OSError, FileNotFoundError
          logger.error('Can not read configuration file.', exc_info=True)
          raise
docs: retrieves box id from the /etc/synergy.conf configuration file
          :raise EnvironmentError: if the configuration file could not be opened
          :raise LookupError: if the configuration file does not define BOX_ID variable