Image download error 500 response

[azu]

I've tested on https://learning.oreilly.com/library/view/distributed-tracing-in/9781492056621/ and get following erros:

[safari-downloader] downloaded chapter files...
[safari-downloader] downloaded stylesheet files...
[safari-downloader] an error occurred while trying to download all the image assets (err: HTTPError: Response code 500 (Internal Server Error))

I've noticed that image downloader does not includes authroized header.
I try to use Safari client and the downloads is successful.

diff --git a/lib/cli/index.js b/lib/cli/index.js
index f223f30..e568811 100644
--- a/lib/cli/index.js
+++ b/lib/cli/index.js
@@ -105,7 +105,7 @@ function start() {
   var safariClient = new Safari(program.debug);
   safariClient.fetchBookById(program.bookid, username, password, cookies, program.weblogin).then( (bookJSON) => {
     // console.log(bookJSON);
-    var ebook = new EbookWriter(bookJSON);
+    var ebook = new EbookWriter(safariClient, bookJSON);
     return ebook.save(program.output);
   }).then( () => {
     // ## finished saving
diff --git a/lib/ebook-writer/index.js b/lib/ebook-writer/index.js
index 3e66341..7ee8052 100644
--- a/lib/ebook-writer/index.js
+++ b/lib/ebook-writer/index.js
@@ -15,12 +15,13 @@ const mime = require('mime');
 * ## eBook Writer
 * sets up the ebook writer with its base settings
 *
+* @param {Safari} safariClient - Safari instance
 * @param {Object} options - the options for the ebook (e.g. content, title, name, etc.)
 *
 * @return {Object} ebook - returns a ebook object
 */
-const Ebook = function Ebook(options) {
-
+const Ebook = function Ebook(safariClient, options) {
+  this.safariClient = safariClient;
   // ## prepare base settings
   this.tempPath = "books";
   this.options = options || {};
@@ -323,7 +324,9 @@ function _writeCSS(that) {
 * @return {Promise} success - returns whether the creation was successful or not
 */
 function _downloadCoverImage(that) {
-  return download(that.options.cover).then( (data) => {
+  return that.safariClient.fetchResource(that.options.cover, {
+    binary: true
+  }).then((data) => {
     debug(`cover image successfully fetched`);
     // ## writing the file to the images directory
     // ## using writeFileSync on purpose; might be using async in the future
@@ -388,14 +391,16 @@ function _prepareImages(that) {
 * ## Download images
 * downloads all the image assets
 *
-* @param {String} that - the ebook object
+* @param {Ebook} that - the ebook object
 *
 * @return {Promise} success - returns whether the creation was successful or not
 */
 function _downloadImages(that) {
   if(!that.options.imagesToFetch) return Promise.reject("there are no images to be fetched yet; prepare first");
   return Promise.all(that.options.imagesToFetch.map( (image) => {
-    return download(image.baseUrl + image.file).then( (data) => {
+    return that.safariClient.fetchResource(image.baseUrl + image.file, {
+      binary: true
+    }).then((data) => {
       // ## the image was successfully downloded, writing to image path
       debug(`${image.file} successfully fetched`);
       // ## writing the file to the images directory
@@ -403,6 +408,9 @@ function _downloadImages(that) {
       let path = that.tempBookPath + "/OEBPS/images/" + image.path;
       fs.writeFileSync(path, data);
       return Promise.resolve();
+    }).catch(error => {
+        debug(`${imagqe.file} failure fetched`);
+        return Promise.reject(error);
     });
   })).then( () => {
     // ## the downloading was successfully finished
diff --git a/lib/safari/index.js b/lib/safari/index.js
index 7211eaa..b65e128 100644
--- a/lib/safari/index.js
+++ b/lib/safari/index.js
@@ -126,18 +126,19 @@ Safari.prototype.fetchResource = function fetchResource(url, options) {
   debug(`fetchResource called with URL: ${url}`);
   if(!url || !this.accessToken && !this.cookieString) return Promise.reject("url was not specified or user has not been authorized yet");
   // ## prepare options for resource request
-  var uri = `${this.baseUrl}/${url}`;
+  var uri = /^https?:/.test(url) ? url : `${this.baseUrl}/${url}`;
   var json = true;
   var headers = {}
   if(this.access_token) headers["authorization"] = `Bearer ${this.accessToken}`
   if(this.cookieString) headers["cookie"] = `${this.cookieString}`
-  if(options && options.json == false) json = false;
+  if(options && (options.json === false || options.binary === true)) json = false;
   if(options && options.uri) uri = options.uri;
   let settings = {
     method: 'GET',
     headers: headers,
     uri: uri,
-    json: json
+    json: json,
+    encoding: options && options.binary ? null : "utf-8"
   };
   // ## make request
   return request(settings).then( (body) => {

However, I just use curl and it is successs.
Maybe, download module is something wrong,

curl https://learning.oreilly.com/library/view/distributed-tracing-in/9781492056621/assets/cover.png -o test.png