Replace unicode() with six.u()

six.u(text)
A fake unicode literal. text should always be a normal string literal.
In Python 2, u() returns unicode, and in Python 3, a string.

Partial Implement: blueprint py33-support

Change-Id: I02849e540c1fbb1f8b02bcbfa4d9be4f60279926
replace basetring/xrange

basetring --> six.string_types
xrange --> six.moves.xrange

Partial Implement: blueprint py33-support

Change-Id: Iedc2cd66ec65c0e4685e56a3bfbf8e9d38fd0072