docs: def read_json_file(fpath):
      """
      Read a JSON file from ``fpath``; raise an exception if it doesn't exist.
  
      :param fpath: path to file to read
      :type fpath: str
      :return: deserialized JSON
      :rtype: dict
      """
      if not os.path.exists(fpath):
          raise Exception('ERROR: file %s does not exist.' % fpath)
      with open(fpath, 'r') as fh:
          raw = fh.read()
      res = json.loads(raw)
      return res