use I18n'ed header on error messages block

app/helpers/devise_helper.rb

@@ -3,7 +3,9 @@ module DeviseHelper
     return "" if resource.errors.empty?
 
     messages = resource.errors.full_messages.map { |msg| content_tag(:li, msg) }.join
-    sentence = "#{pluralize(resource.errors.count, "error")} prohibited this #{resource_name} from being saved:"
+    sentence = I18n.t("errors.messages.not_saved",
+                      :count => resource.errors.count,
+                      :resource => resource_name)
 
     html = <<-HTML
     <div id="error_explanation">
@@ -14,4 +16,4 @@ module DeviseHelper
 
     html.html_safe
   end
-end
+end

config/locales/en.yml

@@ -4,6 +4,9 @@ en:
       not_found: "not found"
       already_confirmed: "was already confirmed"
       not_locked: "was not locked"
+      not_saved:
+        one: "1 error prohibited this %{resource} from being saved:"
+        other: "%{count} errors prohibited this %{resource} from being saved:"
 
   devise:
     failure:

test/integration/registerable_test.rb

@@ -51,6 +51,7 @@ class RegistrationTest < ActionController::IntegrationTest
     assert_have_selector '#error_explanation'
     assert_contain "Email is invalid"
     assert_contain "Password doesn't match confirmation"
+    assert_contain "2 errors prohibited"
     assert_nil User.first
 
     assert_not warden.authenticated?(:user)