Use modern PBR and hacking packages

The pbr release 2.0.0 is breaking in that it removes the use of
warnerrors in build_sphinux. Hacking <0.11 had a similar issue so
use a newer version of that.

Change-Id: I4ad82bb6bf8b2633713dc989445e3d1f318790ee

requirements.txt

@@ -1,7 +1,7 @@
+pbr>=1.8
 alembic>=0.4.1
 oslo.config>=1.4.0.0a3
 oslo.db>=2.1.0,<4.15.0
-pbr>=1.0.0
 python-subunit>=0.0.18
 six>=1.5.2
 SQLAlchemy>=0.8.2

test-requirements.txt

@@ -1,4 +1,4 @@
-hacking>=0.9.2,<0.10
+hacking>=0.12.0,!=0.13.0,<0.14
 coverage>=3.6
 fixtures>=0.3.14
 mock>=1.0