Localhost is working but heroku deploy is not working after adding searchbar for users (heroku run rake db:seed error)

I've added autocompleted searchbar for users to my app ("gem searchkick" and "elasticsearch" were used) then it is great working on localhost. I have also added "SearchBox Elasticsearch -- Starter" to my Heroku app.

After I can push my app to heroku without fail but I've an error with "heroku run db:seed". (The first user can be installed but the second user is not)

How can I fix the problem?

Error

 Running rake db:seed on bloggerpoint... up, run.7859
 ActiveRecord::SchemaMigration Load (1.9ms)  SELECT "schema_migrations".* FROM "schema_migrations"
  (12.7ms)  BEGIN
 User Exists (1.6ms)  SELECT  1 AS one FROM "users" WHERE LOWER("users"."email") = LOWER('example@railstutorial.org') LIMIT 1
 SQL (1.1ms)  INSERT INTO "users" ("name", "email", "password_digest", "admin", "activated", "activated_at", "created_at", "updated_at", "activation_digest") VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9) RETURNING "id"  [["name", "Example User"], ["email", "example@railstutorial.org"], ["password_digest", "$2a$10$tU5lWI6OSivx.9gONACjI.EHDrPgdhyQ9w/5rp6MxitVRpaRilbZu"], ["admin", "t"], ["activated", "t"], ["activated_at", "2015-12-08 20:06:39.898039"], ["created_at", "2015-12-08 20:06:40.199321"], ["updated_at", "2015-12-08 20:06:40.199321"], ["activation_digest", "$2a$10$kI/gNShPNgjz387uCxKBW.XT5OpYOJvL0ayb0G9EXRt6TqxgXjzTm"]]
 (2.0ms)  COMMIT

  User Store (5.9ms)  {"id":1,"exception":["Faraday::ConnectionFailed","Connection refused - connect(2)"]}
 rake aborted!

production.rb

 Elasticsearch::Model.client = Elasticsearch::Client.new host: ENV['search_box_url']

I've made addition to my User model and Gemfile before heroku deploy. My searchbar is working without them on localhost.

user.rb

include Elasticsearch::Model
include Elasticsearch::Model::Callbacks

Gemfile

 group :production do
    gem 'pg',             '0.17.1'
    gem 'rails_12factor', '0.0.2'
    gem 'puma',           '2.11.1'
    gem 'elasticsearch-model'
    gem 'elasticsearch-rails'
 end