Drop py33 support
Drop py33 support

"Python 3.3 support is being dropped since OpenStack Liberty."
written in following URL.
https://wiki.openstack.org/wiki/Python3

And already the infra team and the oslo team are dropping py33
support from their projects.

Since we rely on oslo for a lot of our work, and depend on infra
for our CI, we should drop py33 support too.

Change-Id: I13232c482fc49757bdb242591958c180a3b74b3f
Closes-Bug: #1526170

openstack/python-scciclient,NaohiroTamura/python-scciclient