i18n - Make string translatable

Since internationalization should be enabled in Watcher, this
patchset refactors the Watcher codebase to wrap previously
untranslatable strings with i18n translation functions so we can
import them for translation into the .pot template file.

Partially Implements: blueprint support-translation
Change-Id: I425967a60b5a7957f753894e5d2ba0d2c5009d1d

watcher/decision_engine/strategy/selection/default.py

@@ -17,10 +17,10 @@
 from oslo_config import cfg
 from oslo_log import log
 
-from watcher.common.exception import WatcherException
-from watcher.decision_engine.strategy.loading.default import \
-    DefaultStrategyLoader
-from watcher.decision_engine.strategy.selection.base import BaseSelector
+from watcher._i18n import _
+from watcher.common import exception
+from watcher.decision_engine.strategy.loading import default
+from watcher.decision_engine.strategy.selection import base
 
 LOG = log.getLogger(__name__)
 CONF = cfg.CONF
@@ -41,11 +41,11 @@ CONF.register_group(goals_opt_group)
 CONF.register_opts(WATCHER_GOALS_OPTS, goals_opt_group)
 
 
-class DefaultStrategySelector(BaseSelector):
+class DefaultStrategySelector(base.BaseSelector):
 
     def __init__(self):
         super(DefaultStrategySelector, self).__init__()
-        self.strategy_loader = DefaultStrategyLoader()
+        self.strategy_loader = default.DefaultStrategyLoader()
 
     def define_from_goal(self, goal_name):
         strategy_to_load = None
@@ -54,7 +54,7 @@ class DefaultStrategySelector(BaseSelector):
             return self.strategy_loader.load(strategy_to_load)
         except KeyError as exc:
             LOG.exception(exc)
-            raise WatcherException(
-                "Incorrect mapping: could not find "
-                "associated strategy for '%s'" % goal_name
+            raise exception.WatcherException(
+                _("Incorrect mapping: could not find "
+                  "associated strategy for '%s'") % goal_name
             )