code: def load_config(self, config_path=None):
          
          self.loaded = True
          config = copy.deepcopy(DEFAULTS)
  
          if config_path is None:
              if "FEDORA_MESSAGING_CONF" in os.environ:
                  config_path = os.environ["FEDORA_MESSAGING_CONF"]
              else:
                  config_path = "/etc/fedora-messaging/config.toml"
  
          if os.path.exists(config_path):
              _log.info("Loading configuration from {}".format(config_path))
              with open(config_path) as fd:
                  try:
                      file_config = toml.load(fd)
                      for key in file_config:
                          config[key.lower()] = file_config[key]
                  except toml.TomlDecodeError as e:
                      msg = "Failed to parse {}: error at line {}, column {}: {}".format(
                          config_path, e.lineno, e.colno, e.msg
                      )
                      raise exceptions.ConfigurationException(msg)
          else:
              _log.info("The configuration file, {}, does not exist.".format(config_path))
  
          self.update(config)
          self._validate()
          return self
docs: Load application configuration from a file and merge it with the default
          configuration.
  
          If the ``FEDORA_MESSAGING_CONF`` environment variable is set to a
          filesystem path, the configuration will be loaded from that location.
          Otherwise, the path defaults to ``/etc/fedora-messaging/config.toml``.