Gantt chart is broken for me on master.

I think it's due to this merge.
https://github.com/apache/incubator-airflow/commit/868bc83137adca0ebfd5780f0dff5a7bfdfaadf9

Why is an end_date needed?

Inline image 1

This is the tree view:
Inline image 2

Sumit, as the merger/committer, can you confirm?

-s