Bump hacking to 3.0.0

The new version enables a lot of standard flake8 checks, so a few
fixes are required. W503 is disabled as it conflicts with W504
and the latter seems to be preferred nowadays.

Change-Id: I3b1e20193a2cb3d28046ad0f2008577a95aaaefd
diff --git a/test-requirements.txt b/test-requirements.txt
index 9292937..507278f 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -2,7 +2,7 @@
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
 
-hacking!=0.13.0,<0.14,>=0.12.0 # Apache-2.0
+hacking>=3.0.0,<3.1.0 # Apache-2.0
 
 sphinx!=1.6.6,!=1.6.7,>=1.6.2 # BSD
 openstackdocstheme>=1.20.0 # Apache-2.0