             description = "Error retrieving App Store data as an error was returned."
         case .AppStoreJSONParsingFailure:
             description = "Error parsing App Store JSON data."
+        case .AppStoreOSVersionNumberFailure:
+            description = "Error retrieving iOS version number as there was no data returned."
+        case .AppStoreOSVersionUnsupported:
+            description = "The version of iOS on the device is lower than that of the one required by the app verison update."
         case .AppStoreVersionNumberFailure:
             description = "Error retrieving App Store version number as there was no data returned."
         case .AppStoreVersionArrayFailure:

    case NoUpdateAvailable
    case AppStoreDataRetrievalFailure
    case AppStoreJSONParsingFailure
    case AppStoreVersionNumberFailure
    case AppStoreVersionArrayFailure
    case AppStoreAppIDFailure


                        let jsonData = try NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.AllowFragments)

                        guard let appData = jsonData as? [String: AnyObject]
                            where self.isUpdateCompatibleWithDeviceOS(appData) else {

                            self.postError(.AppStoreJSONParsingFailure, underlyingError: nil)
                            return
                        }
