Update hacking for Python3

The repo is Python 3 now, so update hacking to version 3.0 which
supports Python 3.

Change-Id: Ia544cd6c50fa458b14ca02648338aaecb17b0de9

test-requirements.txt

@@ -3,7 +3,7 @@
 # process, which may cause wedges in the gate later.
 
 bashate>=0.5.1 # Apache-2.0
-hacking!=0.13.0,<0.14,>=0.12.0 # Apache-2.0
+hacking>=3.0,<3.1.0 # Apache-2.0
 
 docutils>=0.11 # OSI-Approved Open Source, Public Domain
 sphinx!=1.6.6,!=1.6.7,>=1.6.2,<2.0.0;python_version=='2.7'  # BSD