Improve error handling

lib/core/createError.js

@@ -0,0 +1,16 @@
+'use strict';
+
+var enhanceError = require('./enhanceError');
+
+/**
+ * Create an Error with the specified message, config, and optional error code.
+ *
+ * @param {string} message The error message.
+ * @param {Object} config The config object.
+ * @param {string} [code] The error code (for example, 'ECONNABORTED').
+ * @returns {Error} The created error.
+ */
+module.exports = function createError(message, config, code) {
+  var error = new Error(message);
+  return enhanceError(error, config, code);
+};

lib/core/enhanceError.js

@@ -0,0 +1,17 @@
+'use strict';
+
+/**
+ * Update an Error with the specified config and optional error code.
+ *
+ * @param {Error} error The error to update.
+ * @param {Object} config The config object.
+ * @param {string} [code] The error code (for example, 'ECONNABORTED').
+ * @returns {Error} The error.
+ */
+module.exports = function enhanceError(error, config, code) {
+  error.config = config;
+  if (code) {
+    error.code = code;
+  }
+  return error;
+};

lib/core/settle.js

@@ -1,5 +1,7 @@
 'use strict';
 
+var createError = require('./createError');
+
 /**
  * Resolve or reject a Promise based on response status.
  *
@@ -13,6 +15,8 @@ module.exports = function settle(resolve, reject, response) {
   if (!response.status || !validateStatus || validateStatus(response.status)) {
     resolve(response);
   } else {
-    reject(response);
+    var error = createError('Request failed with status code ' + response.status, response.config);
+    error.response = response;
+    reject(error);
   }
 };