Switch to internal _i18n pattern, as per oslo_i18n guidelines

Guidelines referenced from:
http://docs.openstack.org/developer/oslo.i18n/usage.html

Change-Id: Ie0984a1fc53d423e541d5dd59ce34f807c8f4513

neutron_taas/extensions/taas.py

@@ -21,6 +21,7 @@ from neutron.api.v2 import resource_helper
 from neutron.common import exceptions as qexception
 from neutron.services import service_base
 
+from neutron_taas._i18n import _
 from neutron_taas.common import constants
 
 from oslo_config import cfg

neutron_taas/services/taas/agents/ovs/agent.py

@@ -24,6 +24,8 @@ from oslo_service import service
 from neutron.agent.common import config
 from neutron.common import config as common_config
 from neutron.common import rpc as n_rpc
+
+from neutron_taas._i18n import _
 from neutron_taas.common import topics
 from neutron_taas.services.taas.agents.ovs import taas_ovs_agent
 

neutron_taas/services/taas/agents/ovs/taas_ovs_agent.py

@@ -15,6 +15,8 @@
 
 
 from neutron.agent.common import config
+
+from neutron_taas._i18n import _
 from neutron_taas.common import topics
 from neutron_taas.services.taas.agents import taas_agent_api as api
 

tox.ini

@@ -48,3 +48,6 @@ show-source = True
 ignore = E123,E125
 builtins = _
 exclude=.venv,.git,.tox,dist,doc,*openstack/common*,*lib/python*,*egg,build
+
+[hacking]
+import_exceptions = neutron_taas._i18n