localize invite model

app/models/invite.rb

@@ -27,7 +27,7 @@ class Invite < ActiveRecord::Base
   # Custom validation: check that email does not already belong to a registered user.
   def email_not_already_registered
     unless User.find_by_email(self.email).nil?
-      errors.add(:email, 'ist bereits in Verwendung. Person ist schon Mitglied der Foodcoop.')
+      errors.add(:email, I18n.t('invites.errors.already_member'))
     end
   end
 

config/locales/de/de.invites.yml

@@ -12,3 +12,7 @@ de:
 
     # used by controller
     success: 'Benutzerin wurde erfolgreich eingeladen.'
+
+    # used by model
+    errors:
+      already_member: 'ist bereits in Verwendung. Person ist schon Mitglied der Foodcoop.'

config/locales/en/en.invites.yml

@@ -13,3 +13,6 @@ en:
     # used by controller
     success: 'User was invited successfully.'
 
+    # used by model
+    errors:
+      already_member: 'is already in use. Person is a member of this Foodcoop already.'