Add externalized strings

app/models/concerns/milestoneish.rb

@@ -87,7 +87,7 @@ module Milestoneish
   end
 
   def total_issue_time_spent
-    issues.joins(:timelogs).sum(:time_spent)
+    @total_issue_time_spent ||= issues.joins(:timelogs).sum(:time_spent)
   end
 
   def human_total_issue_time_spent

app/views/shared/milestones/_sidebar.html.haml

@@ -92,14 +92,14 @@
         - if milestone.human_total_issue_time_spent
           = milestone.human_total_issue_time_spent
         - else
-          None
+          = _("None")
       .title.hide-collapsed
-        Total issue time spent
+        = _("Total issue time spent")
       .value.hide-collapsed
         - if milestone.human_total_issue_time_spent
           %span.bold= milestone.human_total_issue_time_spent
         - else
-          %span.no-value No time spent
+          %span.no-value= _("No time spent")
 
     .block.merge-requests
       .sidebar-collapsed-icon