Python3: define a __next__() method for VerboseIteratorWrapper
Python3: define a __next__() method for VerboseIteratorWrapper

In Python 3, __next__() has replaced next(). Also, call the next() function
rather than the next() method.

Closes-Bug: #1281866
Change-Id: I92b44508c9c875f16ad89ef8410d2c38092ab23d

alexpilotti/python-glanceclient,klmitch/python-glanceclient,klmitch/python-glanceclient,openstack/python-glanceclient,JioCloud/python-glanceclient,mmasaki/python-glanceclient,mmasaki/python-glanceclient,alexpilotti/python-glanceclient,varunarya10/python-glanceclient,openstack/python-glanceclient,JioCloud/python-glanceclient,varunarya10/python-glanceclient