Handle authentication failure callbacks with no message

app/controllers/users_controller.rb

@@ -335,7 +335,7 @@ class UsersController < ApplicationController
   ##
   # omniauth failure callback
   def auth_failure
-    flash[:error] = t("users.auth_failure.#{params[:message]}")
+    flash[:error] = t(params[:message], :scope => "users.auth_failure", :default => t("users.auth_failure.unknown_error"))
     redirect_to params[:origin] || login_url
   end
 

config/locales/en.yml

@@ -2623,6 +2623,7 @@ en:
       no_authorization_code: No authorization code
       unknown_signature_algorithm: Unknown signature algorithm
       invalid_scope: Invalid scope
+      unknown_error: Authentication failed
     auth_association:
       heading: Your ID is not associated with a OpenStreetMap account yet.
       option_1: |