unit-test: Switch to python3
unit-test: Switch to python3

The change was generated using 2to3-2.7 and then tweaked to fix the
string encoding/decoding.

Change-Id: Iabeb7dc1ef4edf6ada710de752b19b5a71c6187c
Signed-off-by: Andrew Jeffery <02e0a999c50b1f88df7a8f5a04e1b76b35ea6a88@aj.id.au>

openbmc/openbmc-build-scripts,openbmc/openbmc-build-scripts