creating an event (impression) for an unassigned user gives a 201 response code

[sudheerkethireddy]

          I have created an experiment within an app. I tried creating an impression for a user without assigning the user to any bucket. The Api gives 201 as response code rather than throwing some warning/error saying that the user is not assigned.

Steps to re-produce.

1. create an App (if not existing)
2. create an experiment within the application.
3. create buckets
4. do a Post call to submit an event (of type impression) and it returns 201.