Internationalization (i18n) - Enable French locale

Our project should now enable its internationalization.
This patchset add the french locale to the project but also
refactors the codebase to following the oslo_i18n recommendations.

DocImpact
Implements: blueprint support-translation

Change-Id: I0e4fbf05d16afb5e25bac78438c640f147c754b1

watcher/cmd/api.py

@@ -24,8 +24,8 @@ from wsgiref import simple_server
 from oslo_config import cfg
 from oslo_log import log as logging
 
+from watcher._i18n import _
 from watcher.api import app as api_app
-from watcher.common.i18n import _
 from watcher import service
 
 

watcher/cmd/applier.py

@@ -24,13 +24,13 @@ import sys
 from oslo_config import cfg
 from oslo_log import log as logging
 
+from watcher import _i18n
 from watcher.applier.manager import ApplierManager
 from watcher.common import service
-from watcher import i18n
 
 LOG = logging.getLogger(__name__)
 CONF = cfg.CONF
-_LI = i18n._LI
+_LI = _i18n._LI
 
 
 def main():

watcher/cmd/decisionengine.py

@@ -23,15 +23,15 @@ import sys
 
 from oslo_config import cfg
 from oslo_log import log as logging
+
+from watcher import _i18n
 from watcher.common import service
 from watcher.decision_engine.manager import DecisionEngineManager
 
-from watcher import i18n
-
 
 LOG = logging.getLogger(__name__)
 CONF = cfg.CONF
-_LI = i18n._LI
+_LI = _i18n._LI
 
 
 def main():