herokuにデプロイする上で躓いた事①（sqlite以外をbundleする時）

＃問題点h1
herokuにはsqliteは使えず、pgを使うとの事だが上手くいかない。

＃解決策h2
gemfile内に
group :production do
    gem 'pg', '~> 0.20'
    gem 'rails_12factor'
end

group :development, :test do
    gem 'sqlite3',      '1.3.13'
end

group :development, :test do
  gem 'byebug', '9.0.6', platform: :mri
end

group :development do
  gem 'web-console',           '3.5.1'
  gem 'listen',                '3.0.8'
  gem 'spring',                '2.0.2'
  gem 'spring-watcher-listen', '2.0.1'
end

productiongropとdevelopmentgroupを作り下記を実行。

Bundle complete! 25 Gemfile dependencies, 82 gems now installed.
Gems in the groups production and development were not installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.
↓
↓
↓
↓
↓
bundle install --without production　
Bundle ! 25 Gemfile dependencies, 91 gems now installed.
Gems in the group production were not installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.



$ git push heroku master
remote: -----> Installing dependencies using bundler 1.15.2
remote:        Running: bundle install --without development:test --path vendor/bundle --binstubs vendor/bundle/bin -j4 --deployment
remote:        Warning: the running version of Bundler (1.15.2) is older than the version that created the lockfile (1.16.1). We suggest you upgrade to the latest version of Bundler by running `gem install bundler`.

remote:        Bundle complete! 25 Gemfile dependencies, 84 gems now installed.
remote:        Gems in the groups development and test were not installed.
remote:        Bundled gems are installed into ./vendor/bundle.
remote:        Post-install message from paperclip:
remote:        ##################################################
remote:        #  NOTE FOR UPGRADING FROM 4.3.0 OR EARLIER       #
remote:        ##################################################
remote:        Paperclip is now compatible with aws-sdk >= 2.0.0.
remote:        If you are using S3 storage, aws-sdk >= 2.0.0 requires you to make a few small
remote:        changes:
remote:        * You must set the `s3_region`
remote:        * If you are explicitly setting permissions anywhere, such as in an initializer,
remote:        note that the format of the permissions changed from using an underscore to
remote:        using a hyphen. For example, `:public_read` needs to be changed to
remote:        `public-read`.
remote:        For a walkthrough of upgrading from 4 to 5 and aws-sdk >= 2.0 you can watch
remote:        http://rubythursday.com/episodes/ruby-snack-27-upgrade-paperclip-and-aws-sdk-in-prep-for-rails-5
remote:        Bundle completed (29.23s)
remote:        Cleaning up the bundler cache.
remote: -----> Installing node-v6.11.1-linux-x64
remote: -----> Detecting rake tasks
remote: -----> Preparing app for Rails asset pipeline
remote:        Running: rake assets:precompile
remote:        rake aborted!
remote:        Gem::LoadError: Specified 'postgresql' for database adapter, but the gem is not loaded. Add `gem 'pg'` to your Gemfile (and ensure its version is at the minimum required by ActiveRecord).

↓↓↓↓↓↓

gemfile内の gem "pg" を　gem 'pg', '~> 0.20'
に変えることによってエラー取れた。
git push heroku master　完了。

参考：https://stackoverflow.com/questions/39261996/heroku-and-rails-gem-load-error-with-postgres-however-it-is-specified-in-gemfi