Parse response_body and flesh out attributes

lib/MailchimpMarketing/api_error.rb

@@ -10,27 +10,40 @@
 
 =end
 
+require 'json'
+
 module MailchimpMarketing
   class ApiError < StandardError
     attr_reader :status, :type, :title, :detail, :instance, :errors
 
-    attr_reader :response_headers, :response_body
+    attr_reader :response_headers, :response_body, :parsed_response_body
 
     # Usage examples:
     #   ApiError.new
     #   ApiError.new("message")
     #   ApiError.new(:status => 500, :response_headers => {}, :response_body => "")
     #   ApiError.new(:status => 404, :message => "Not Found")
     def initialize(arg = nil)
-      if arg.is_a? Hash
-        if arg.key?(:message) || arg.key?('message')
-          super(arg[:message] || arg['message'])
+      if arg.is_a?(Hash)
+        arg.transform_keys!(&:to_sym)
+
+        if arg.key?(:message)
+          super(arg[:message])
+        elsif arg.key?(:response_body)
+          @parsed_response_body = JSON.parse(arg[:response_body] ).transform_keys!(&:to_sym)
+          super parsed_response_body[:title]
         else
           super arg
         end
 
-        arg.each do |k, v|
-          instance_variable_set "@#{k}", v
+        if parsed_response_body && parsed_response_body[:errors].is_a?(Array)
+          parsed_response_body[:errors].map do |error|
+            error.transform_keys!(&:to_sym)
+          end
+        end
+
+        arg.merge(parsed_response_body || {}).each do |k, v|
+          instance_variable_set("@#{k}", v)
         end
       else
         super arg