title: How to Trigger a Task based on previous task status?
body: <p>I have 4 tasks as shown below. I want Task D to be triggered even if Task C has Failed or Succeeded. However, Task C or Task D should not be triggered if Task A or Task B has failed.</p>
  <p>I tried to use trigger rule = all_done for Task D but if Task B fails, it triggers Task D as well.</p>
  <p><a href="https://i.stack.imgur.com/egZig.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/egZig.png" alt="dag" /></a></p>
  <p>Is there a way to accomplish this in  Airflow?</p>