Find -> (node:1976) Warning: a promise was created in a handler but was not returned from it

How to find where promise is created and not returned. I am using bluebird.

(node:1976) Warning: a promise was created in a handler but was not returned from it

I know we can ignore this warning by adding BLUEBIRD_W_FORGOTTEN_RETURN=0 in my environment. I am more interested in to find where it is coming from.

via Satyam Koyani