Fatal error: Interface 'Drupal\page_manager\Plugin\ContextAwareVariantInterface' not found in

After update to latest code, Drupal 8.0.0 -RC1,
Page Manager :8.x-1.0-alpha17
Ctools, latest devel version.

I got following error:
Fatal error: Interface 'Drupal\page_manager\Plugin\ContextAwareVariantInterface' not found in D:\xampp\htdocs\tianjin\modules\panels\src\Plugin\DisplayVariant\PanelsDisplayVariant.php on line 43

It seems that ContextAwareVariantInterface be removed from page_manager.

I use the old version of page_manager, Ctools, which works very well with Drupal8.0.0-beta15,
After I update to Drupal 8.0.0 -RC1, it does not work at all.