message: Add cancel button to error stage
diff: @@ -181,12 +181,15 @@ export default React.createClass({
  let content;
  if (this.state.error) {
  + const DialogButtons = sdk.getComponent('views.elements.DialogButtons');
  content = <div>
  <p>{_t("Unable to create key backup")}</p>
  <div className="mx_Dialog_buttons">
  - <button onClick={this._createBackup}>
  - {_t("Retry")}
  - </button>
  + <DialogButtons primaryButton={_t('Retry')}
  + onPrimaryButtonClick={this._createBackup}
  + hasCancel={true}
  + onCancel={this._onCancel}
  + />
  </div>
  </div>;
  } else {
  