reject from API return proper Error object

frontend-js/src/main/js/ServerConnector.js

@@ -101,7 +101,8 @@ ServerConnector._readFile = function(url) {
         reject(error);
 
       } else if (response.statusCode !== 200) {
-        reject(response);
+        var error = new Error(url + " rejected with status code: " + response.statusCode);
+        reject(error);
       } else {
         resolve(body);
       }
@@ -119,7 +120,8 @@ ServerConnector.sendPostRequest = function(url, params) {
         reject(error);
 
       } else if (response.statusCode !== 200) {
-        reject(response);
+        var error = new Error(url + " rejected with status code: " + response.statusCode);
+        reject(error);
       } else {
         resolve(body);
       }
@@ -136,7 +138,8 @@ ServerConnector.sendPutRequest = function(url, params) {
       if (error) {
         reject(error);
       } else if (response.statusCode !== 200) {
-        reject(response);
+        var error = new Error(url + " rejected with status code: " + response.statusCode);
+        reject(error);
       } else {
         resolve(body);
       }
@@ -154,7 +157,8 @@ ServerConnector.sendDeleteRequest = function(url, params) {
       if (error) {
         reject(error);
       } else if (response.statusCode !== 200) {
-        reject(response);
+        var error = new Error(url + " rejected with status code: " + response.statusCode);
+        reject(error);
       } else {
         resolve(body);
       }
@@ -172,7 +176,8 @@ ServerConnector.sendPatchRequest = function(url, params) {
       if (error) {
         reject(error);
       } else if (response.statusCode !== 200) {
-        reject(response);
+        var error = new Error(url + " rejected with status code: " + response.statusCode);
+        reject(error);
       } else {
         resolve(body);
       }