Devise login with username, signin failure not showing error message

I have been trying to login with username so followed this tutorial

http://ift.tt/1f1PJgz

Sign in with username and signup is happening perfectly. But if i try to sign in with invalid username or password, it is not showing any error messages.

i have <%= devise_error_messages! %> mentioned in sessions/new.html.erb. Also tried binding.pry resource doesn't have any errors attached to it.

routes.rb

devise_for :users
devise_scope :user do
  root to: "devise/sessions#new"
end

devise.rb

config.authentication_keys = [ :login ]

other details same as mentioned in the url.