text: function(eventCollection) {
    var onHeadersReceivedEvent = eventCollection.firstEventOfType('onHeadersReceived');
    if (!onHeadersReceivedEvent) { return null; }
    var { statusCode, responseHeaders: { location } } = onHeadersReceivedEvent;
    return Number(statusCode) !== 200 ? this.createResult(5, 'HTTP', `HTTP ${statusCode} -> ${location}`, 'warning') : null;
  }
  