def __init__()

in pystemd/dbusexc.pyx [0:0]


    def __init__(self, errno, err_name=None, err_message=None):
      is_base_error = self.__class__.__name__ == 'DBusBaseError'
      custom_msg = (
        "\nThis is DBusBaseError, a base error for DBus (i bet you did not "
        "see that coming) if you need a special error, enhance "
        "pystemd.sysdexc module!."
      ) if is_base_error else ''

      self.errno = errno
      self.err_name = (err_name or '') if is_base_error else ''
      self.err_message = err_message or ''

      super(DBusBaseError, self).__init__(
            '%s[err %s]: %s%s' % (self.err_name,
                              self.errno,
                              self.err_message, custom_msg))