Username not required to create a new user, but if blank receive duplicate username errror

Overview:  This was reported by testers of Juniper, and confirmed by Holly.  **  This is not the behavior in Iris. In Iris the new user is saved without a Username.

Steps to Reproduce:

1. Log into Juniper BugFest as an admin.
2. Open Users app.
3. Select +New from Actions menu.
4. Enter in only the required fields, which does not include Username.
5. Save the user.

Expected Results:  New user is saved without a Username, as is done with Iris.

Actual Results:  Receive system error as shown in attached screen print Duplicate-username-error.jpg.

Additional Information:  I have been told that this is reproducible in SNAPSHOT.

Interested parties: