Update hacking for Python3

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

Fix problems found.

Change-Id: Ia59a23a36ebb8548a20e894000f7342c73012eac
diff --git a/.zuul.yaml b/.zuul.yaml
index d958843..4af2e62 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -27,6 +27,7 @@
       devstack_plugins:
         barbican: https://opendev.org/openstack/barbican
       devstack_localrc:
+        USE_PYTHON3: true
         NOVA_BACKEND: LVM
         LVM_VOLUME_CLEAR: none
       devstack_local_conf: