D8 entity annotation exception

When using annotation in D8 (e.g. when creating an entity), there are a couple classes annotation depends on. If you do not use them, you will get an exception that looks a little like this:

If you have just changed code (for example deployed a new module or moved an existing one) read http://drupal.org/documentation/rebuild
Additional uncaught exception thrown while handling exception.

I am pointing this out because confusion could be had if your IDE points out which classes you import but are not used. PHPStorm does not understand the annotation classes are required, so it will gray them out. It is tempting to remove things that are grayed out. (for me!)

Adding these may resolve the issue if it's annotation related.

use Drupal\Core\Entity\Annotation\EntityType;
use Drupal\Core\Annotation\Translation;

I wanted to post in hopes that the search gods will pick this up for anyone stuck in that rut.