python3: Fix unicode strings

Python3 enforces the distinction between byte
strings and text strings more rigorously than
python2. So use six.text_type where approiate.

Change-Id: I46b3f5fe1f990fc1b7a3ee32904d608b070fc4c3
Signed-off-by: Chuck Short <chuck.short@canonical.com>
Merge "python3: Fix unicode strings"