herokuへのデプロイ

前提・実現したいこと

herokuにデプロイしたいのですが、上手くいきません。
データベース情報をmysql2に上書きした後、「git push heroku master」をGit bush上で実行し、「heroku run rake db:migrate」を実行した時点で上手くいかなくなりました。

原因がわかる方、教えて頂けると嬉しいです。

発生している問題・エラーメッセージ

We're sorry, but something went wrong.
If you are the application owner check the logs for more information.

該当のソースコード

WARNING: This is the legacy Heroku CLI with limited functionality. Please install the latest CLI.
WARNING: Installation instructions are at https://cli.heroku.com
Running rake db:migrate on ⬢ hidden-depths-41257... up, run.5564 (Free)
rake aborted!
Mysql2::Error: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)
/app/vendor/bundle/ruby/2.3.0/gems/mysql2-0.3.18/lib/mysql2/client.rb:70:in connect' /app/vendor/bundle/ruby/2.3.0/gems/mysql2-0.3.18/lib/mysql2/client.rb:70:in initialize'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/connection_adapters/mysql2_adapter.rb:18:in new' /app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/connection_adapters/mysql2_adapter.rb:18:in mysql2_connection'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:438:in new_connection' /app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:448:in checkout_new_connection'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:422:in acquire_connection' /app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:349:in block in checkout'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:348:in checkout' /app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:263:in block in connection'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:262:in connection' /app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:571:in retrieve_connection'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/connection_handling.rb:113:in retrieve_connection' /app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/connection_handling.rb:87:in connection'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/migration.rb:916:in initialize' /app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/migration.rb:823:in new'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/migration.rb:823:in up' /app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/migration.rb:801:in migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/tasks/database_tasks.rb:137:in migrate' /app/vendor/bundle/ruby/2.3.0/gems/activerecord-4.2.5/lib/active_record/railties/databases.rake:44:in block (2 levels) in <top (required)>'
/app/vendor/bundle/ruby/2.3.0/gems/rake-12.0.0/exe/rake:27:in <top (required)>' /app/vendor/bundle/ruby/2.3.0/gems/bundler-1.15.2/lib/bundler/cli/exec.rb:74:in load'
/app/vendor/bundle/ruby/2.3.0/gems/bundler-1.15.2/lib/bundler/cli/exec.rb:74:in kernel_load' /app/vendor/bundle/ruby/2.3.0/gems/bundler-1.15.2/lib/bundler/cli/exec.rb:27:in run'
/app/vendor/bundle/ruby/2.3.0/gems/bundler-1.15.2/lib/bundler/cli.rb:360:in exec' /app/vendor/bundle/ruby/2.3.0/gems/bundler-1.15.2/lib/bundler/vendor/thor/lib/thor/command.rb:27:in run'
/app/vendor/bundle/ruby/2.3.0/gems/bundler-1.15.2/lib/bundler/vendor/thor/lib/thor/invocation.rb:126:in invoke_command' /app/vendor/bundle/ruby/2.3.0/gems/bundler-1.15.2/lib/bundler/vendor/thor/lib/thor.rb:369:in dispatch'
/app/vendor/bundle/ruby/2.3.0/gems/bundler-1.15.2/lib/bundler/cli.rb:20:in dispatch' /app/vendor/bundle/ruby/2.3.0/gems/bundler-1.15.2/lib/bundler/vendor/thor/lib/thor/base.rb:444:in start'
/app/vendor/bundle/ruby/2.3.0/gems/bundler-1.15.2/lib/bundler/cli.rb:10:in start' /app/vendor/bundle/ruby/2.3.0/gems/bundler-1.15.2/exe/bundle:30:in block in <top (required)>'
/app/vendor/bundle/ruby/2.3.0/gems/bundler-1.15.2/lib/bundler/friendly_errors.rb:121:in with_friendly_errors' /app/vendor/bundle/ruby/2.3.0/gems/bundler-1.15.2/exe/bundle:22:in <top (required)>'
/app/bin/bundle:3:in load' /app/bin/bundle:3:in <main>'
Tasks: TOP => db:migrate
(See full trace by running task with --trace)

試したこと

補足情報(言語/FW/ツール等のバージョンなど)