###わからないこと
cloud9でRubyのsinatraの学習を行っており下記URLの手順通り進めているのですが、
creare_tableまでは正常に行けるのですが、
bundle exec rake db:migrate左記のコマンドを実行してもmigrateが作成できません。

【https://github.com/janko-m/sinatra-activerecord】

###発生している問題・エラーメッセージ
rake aborted!
ActiveRecord::ConnectionNotEstablished: No connection pool with 'primary' found.
/home/ubuntu/workspace/vendor/bundle/ruby/2.4.0/gems/activerecord-5.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:930:in retrieve_connection' /home/ubuntu/workspace/vendor/bundle/ruby/2.4.0/gems/activerecord-5.1.4/lib/active_record/connection_handling.rb:116:in retrieve_connection'
/home/ubuntu/workspace/vendor/bundle/ruby/2.4.0/gems/activerecord-5.1.4/lib/active_record/connection_handling.rb:88:in connection' /home/ubuntu/workspace/vendor/bundle/ruby/2.4.0/gems/activerecord-5.1.4/lib/active_record/schema_migration.rb:20:in table_exists?'
/home/ubuntu/workspace/vendor/bundle/ruby/2.4.0/gems/activerecord-5.1.4/lib/active_record/schema_migration.rb:24:in create_table' /home/ubuntu/workspace/vendor/bundle/ruby/2.4.0/gems/activerecord-5.1.4/lib/active_record/migration.rb:1125:in initialize'
/home/ubuntu/workspace/vendor/bundle/ruby/2.4.0/gems/activerecord-5.1.4/lib/active_record/migration.rb:1007:in new' /home/ubuntu/workspace/vendor/bundle/ruby/2.4.0/gems/activerecord-5.1.4/lib/active_record/migration.rb:1007:in up'
/home/ubuntu/workspace/vendor/bundle/ruby/2.4.0/gems/activerecord-5.1.4/lib/active_record/migration.rb:985:in migrate' /home/ubuntu/workspace/vendor/bundle/ruby/2.4.0/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:171:in migrate'
/home/ubuntu/workspace/vendor/bundle/ruby/2.4.0/gems/activerecord-5.1.4/lib/active_record/railties/databases.rake:58:in block (2 levels) in <top (required)>' /home/ubuntu/workspace/vendor/bundle/ruby/2.4.0/gems/rake-12.1.0/exe/rake:27:in <top (required)>'
/usr/local/rvm/gems/ruby-2.4.0/gems/bundler-1.15.4/lib/bundler/cli/exec.rb:74:in load' /usr/local/rvm/gems/ruby-2.4.0/gems/bundler-1.15.4/lib/bundler/cli/exec.rb:74:in kernel_load'
/usr/local/rvm/gems/ruby-2.4.0/gems/bundler-1.15.4/lib/bundler/cli/exec.rb:27:in run' /usr/local/rvm/gems/ruby-2.4.0/gems/bundler-1.15.4/lib/bundler/cli.rb:362:in exec'
/usr/local/rvm/gems/ruby-2.4.0/gems/bundler-1.15.4/lib/bundler/vendor/thor/lib/thor/command.rb:27:in run' /usr/local/rvm/gems/ruby-2.4.0/gems/bundler-1.15.4/lib/bundler/vendor/thor/lib/thor/invocation.rb:126:in invoke_command'
/usr/local/rvm/gems/ruby-2.4.0/gems/bundler-1.15.4/lib/bundler/vendor/thor/lib/thor.rb:387:in dispatch' /usr/local/rvm/gems/ruby-2.4.0/gems/bundler-1.15.4/lib/bundler/cli.rb:22:in dispatch'
/usr/local/rvm/gems/ruby-2.4.0/gems/bundler-1.15.4/lib/bundler/vendor/thor/lib/thor/base.rb:466:in start' /usr/local/rvm/gems/ruby-2.4.0/gems/bundler-1.15.4/lib/bundler/cli.rb:13:in start'
/usr/local/rvm/gems/ruby-2.4.0/gems/bundler-1.15.4/exe/bundle:30:in block in <top (required)>' /usr/local/rvm/gems/ruby-2.4.0/gems/bundler-1.15.4/lib/bundler/friendly_errors.rb:121:in with_friendly_errors'
/usr/local/rvm/gems/ruby-2.4.0/gems/bundler-1.15.4/exe/bundle:22:in <top (required)>' /usr/local/rvm/gems/ruby-2.4.0/bin/bundle:22:in load'
/usr/local/rvm/gems/ruby-2.4.0/bin/bundle:22:in <main>' /usr/local/rvm/gems/ruby-2.4.0/bin/ruby_executable_hooks:15:in eval'
/usr/local/rvm/gems/ruby-2.4.0/bin/ruby_executable_hooks:15:in `<main>'
Tasks: TOP => db:migrate
(See full trace by running task with --trace)

【Rakefile】

Rakefile

require "sinatra/activerecord/rake"

namespace :db do
task :load_config do
require "./app"
end
end

【Gemfile】

frozen_string_literal: true

source "https://rubygems.org"

gem 'sinatra'
gem 'sinatra-reloader'
gem "sinatra-activerecord"
gem "sqlite3"
gem "rake"

gem "rails"

【20170918080428_create_contacts】
class CreateContacts < ActiveRecord::Migration[5.1]
def change
create_table :contacts do |t|
t.string :name
end
end
end
bundle exec rake db:migrate

【app.rb】
require 'rubygems'
require 'bundler'

Bundler.require

set :database, {adapter: "sqlite3", database: "contacts.sqlite3"}

get '/' do
@now = Time.now
erb :index
end

get '/contact_new' do
erb :contact_form
end

post '/contacts' do
puts "###これはテストです"
p params
redirect '/'
end

曖昧な表現が多いですが、ご回答宜しくお願い致します。