Python3: do not use the 'file' type
Python3: do not use the 'file' type

It does not exist in Python 3, so we have to use a workaround.

Change-Id: Ib41b5d12102707004b354835265861710aaba568
Closes-Bug: 1287728

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