Deploy error in Heroku

gistfile1.txt

Olá pessoal,

Estou tendo problemas com esta aplicação que estou fazendo deploy para o Heroku.

Lendo o último log que compartilho abaixo, o problema para ser com a versão do Bundler. Já fiz algumas mudanças
e até rodei o "gem install bundle --pre" e por enquanto não deu certo, a aplicação não roda. 
Vejam no link  https://agenda-contatos-app.herokuapp.com/


Last log application:
-----> Ruby app detected
-----> Compiling Ruby/Rails
-----> Using Ruby version: ruby-2.4.1
-----> Installing dependencies using bundler 1.15.2
       Running: bundle install --without development:test --path vendor/bundle --binstubs vendor/bundle/bin -j4 --deployment
       Warning: the running version of Bundler (1.15.2) is older than the version that created the lockfile (1.16.0.pre.2). We suggest you upgrade to the latest version of Bundler by running `gem install bundler --pre`.
       Fetching gem metadata from https://rails-assets.org/..
       Fetching gem metadata from https://rubygems.org/.........
       Fetching version metadata from https://rails-assets.org/..
       Fetching version metadata from https://rubygems.org/..
       Fetching dependency metadata from https://rails-assets.org/..
       Fetching dependency metadata from https://rubygems.org/.
       Fetching gem metadata from https://rails-assets.org/..
       Fetching version metadata from https://rails-assets.org/.
       Using rake 12.1.0
       Using concurrent-ruby 1.0.5
       Using i18n 0.8.6
       Using minitest 5.10.3
       Using thread_safe 0.3.6
       Using builder 3.2.3
       Using erubi 1.6.1
       Using mini_portile2 2.3.0
       Using crass 1.0.2
       Using rack 2.0.3
       Using nio4r 2.1.0
       Using websocket-extensions 0.1.2
       Using mime-types-data 3.2016.0521
       Using arel 8.0.0
       Using kaminari-core 1.0.1
       Using bundler 1.15.2
       Using method_source 0.9.0
       Using thor 0.20.0
       Using cocoon 1.2.10
       Using coffee-script-source 1.12.2
       Using execjs 2.7.0
       Using commonjs 0.2.7
       Using ffi 1.9.18
       Using multi_json 1.12.2
       Using tilt 2.0.8
       Using pg 0.21.0
       Using puma 3.10.0
       Using rails-assets-notifyjs 0.4.2
       Using rails_serve_static_assets 0.0.5
       Using rails_stdout_logging 0.0.5
       Using rb-fsevent 0.10.2
       Using turbolinks-source 5.0.3
       Using nokogiri 1.8.1
       Using tzinfo 1.2.3
       Using websocket-driver 0.6.5
       Using mime-types 3.1
       Using rack-test 0.7.0
       Using sprockets 3.7.1
       Using less 2.6.0
       Using rb-inotify 0.9.10
       Using rails_12factor 0.0.3
       Using turbolinks 5.0.1
       Using coffee-script 2.4.1
       Using uglifier 3.2.0
       Using loofah 2.1.1
       Using mail 2.6.6
       Using activesupport 5.1.4
       Using sass-listen 4.0.0
       Using rails-html-sanitizer 1.0.3
       Using rails-dom-testing 2.0.3
       Using globalid 0.4.0
       Using activemodel 5.1.4
       Using jbuilder 2.7.0
       Using sass 3.5.1
       Using actionview 5.1.4
       Using activejob 5.1.4
       Using activerecord 5.1.4
       Using actionpack 5.1.4
       Using kaminari-actionview 1.0.1
       Using kaminari-activerecord 1.0.1
       Using actioncable 5.1.4
       Using actionmailer 5.1.4
       Using railties 5.1.4
       Using sprockets-rails 3.2.1
       Using less-rails 2.8.0
       Using kaminari 1.0.1
       Using rails 5.1.4
       Using coffee-rails 4.2.2
       Using jquery-rails 4.3.1
       Using rails-i18n 5.0.4
       Using twitter-bootstrap-rails 4.0.0
       Using sass-rails 5.0.6
       Using bootstrap4-kaminari-views 1.0.0
       Bundle complete! 27 Gemfile dependencies, 73 gems now installed.
       Gems in the groups development and test were not installed.
       Bundled gems are installed into ./vendor/bundle.
       The latest bundler is 1.16.0.pre.2, but you are currently running 1.15.2.
       To update, run `gem install bundler --pre`
       Bundle completed (4.63s)
       Cleaning up the bundler cache.
       Warning: the running version of Bundler (1.15.2) is older than the version that created the lockfile (1.16.0.pre.2). We suggest you upgrade to the latest version of Bundler by running `gem install bundler --pre`.
       The latest bundler is 1.16.0.pre.2, but you are currently running 1.15.2.
       To update, run `gem install bundler --pre`
-----> Installing node-v6.11.1-linux-x64
-----> Detecting rake tasks
-----> Preparing app for Rails asset pipeline
       Running: rake assets:precompile
       Yarn executable was not detected in the system.
       Download Yarn at https://yarnpkg.com/en/docs/install
       Asset precompilation completed (1.60s)
       Cleaning assets
       Running: rake assets:clean
-----> Discovering process types
       Procfile declares types     -> web
       Default types for buildpack -> console, rake, worker
-----> Compressing...
       Done: 36.3M
-----> Launching...
       Released v7
       https://agenda-contatos-app.herokuapp.com/ deployed to Heroku