function assertErrorPageVisible(container, message, recoverable) {
  const element = dom.getElementByClass(
      'firebaseui-id-page-recoverable-error', container);
  assertNotNull(element);
  const msgContainer = dom.getElementByClass('firebaseui-text', container);
  assertContains(message, dom.getTextContent(msgContainer));
  const retryButton = getRetryButton(container);
  if (recoverable) {
    assertNotNull(retryButton);
  } else {
    assertNull(retryButton);
  }
}
Asserts the error page is visible and it contains the correct error message.
@param {!Element} container The html element container of the widget.
@param {string} message The error message.
@param {boolean} recoverable Whether the error is recoverable.