devise_for :users, :controllers => { :sessions=>"sessions", :registrations => "registrations" }, :path => "users", :path_names => { :sign_in => "login", :sign_out => "logout", :sign_up => "register" }

class SessionsController < Devise::SessionsController
  def create
    begin
      if do_some_other_checks
        super
      else
        build_resource
        clean_up_passwords(resource)
        flash[:alert] = "Login error"
        render :new
      end
    rescue => e
        build_resource
        clean_up_passwords(resource)
        flash[:alert] = "Login error"
        render :new
    end
  end
end