python3: Use from future import unicode_literals

use  "from future import unicode_literals" instead of u""

To the road to Python3, a possible next step would be to use the from __future__ import unicode_literals
and remove the u'' prefixes, as it is not supported in Python3.

Change-Id: Ic7afb3cf2d8dfad47b8a1626ab264f6d4f50d00e
Signed-off-by: Chuck Short <chuck.short@canonical.com>
Merge "python3: Use from future import unicode_literals"