code: function fetchText(address, contentType) {
      return get(address, contentType)
          .then(streamToText)
          .catch(err => {
              console.error(`Fetch error: ${err.message}`);
              throw err; // re-throw
          });
  }
docs: Fetches text from the given address.
  Rejects if received text is larger than MAX_TEXT_LENGTH.
  
  @param {string} address source URL
  @param {string?} [contentType] expected content type or undefined if any
  @returns {Promise<string>} resulting text