Fix unicode error for python3
Fix unicode error for python3

Fix undefined name 'unicode' errors when python3 is used.

Change-Id: I6803a1e5154c3815bd57392272630aac689f13fb
Signed-off-by: Ranler Cao <d43306d47c0985094e266a10373b83532df4bd2d@fiberhome.com>

kevin-zhaoshuai/zun,kevin-zhaoshuai/zun,kevin-zhaoshuai/zun