Updated openstack/openstack
Project: openstack/keystone  83c7805ed3787303f8497bc479469d9071783107

Fixes a Python3 syntax error

Python3 has a new way to raise an exception with an existing traceback.
In Python2 there was a special syntax, but that was removed in Python3.

bp python3

Change-Id: I6811f7f46693fc84d0c61116cdd4897b6c20a9fc