Fix pep8 failure on py3
Fix pep8 failure on py3

pep8 check failed on python3 like

./stackalytics/dashboard/vault.py:48:30: F821 undefined name 'basestring'
        if not isinstance(o, basestring):
./stackalytics/dashboard/vault.py:51:20: F821 undefined name 'intern'
            return intern(o)
./stackalytics/dashboard/vault.py:52:26: F821 undefined name 'unicode'
        if isinstance(o, unicode):
                         ^

This patch fixes it by merging 2 versions of uniintern() into a single
method which supports both PY2 and PY3.

Change-Id: Ib18fcfffcdcc8628e7bca5b3558667fb371c956d

stackforge/stackalytics,0xf2/stackalytics,stackforge/stackalytics,stackforge/stackalytics,0xf2/stackalytics,0xf2/stackalytics,0xf2/stackalytics,openstack/stackalytics,openstack/stackalytics,openstack/stackalytics,openstack/stackalytics