Add TASK_ERROR reason code

src/boxerror.js

@@ -45,6 +45,7 @@ BoxError.LOGROTATE_ERROR = 'Logrotate Error';
 BoxError.NETWORK_ERROR = 'Network Error';
 BoxError.NOT_FOUND = 'Not found';
 BoxError.REVERSEPROXY_ERROR = 'ReverseProxy Error';
+BoxError.TASK_ERROR = 'Task Error';
 
 BoxError.prototype.toPlainObject = function () {
     return _.extend({}, { message: this.message, reason: this.reason }, this.details);