title: Why does the Heroku Rails App crash after upgrading Rails to 6.0.0?
body: <p>I have an application that I successfully uploaded to Heroku and everything worked fine. After updating with the <code>rails app:update</code> command from version 6.0.0rc1 to 6.0.0, I deployed the application to heroku and after that the Heroku is crashed when the server launch.</p>
  
  <pre><code>2019-08-20T12:45:56.047319+00:00 heroku[web.1]: State changed from crashed to starting
  2019-08-20T12:46:01.995009+00:00 heroku[web.1]: Starting process with command `bundle exec puma -t 5:5 -p ${PORT:-3000} -e ${RACK_ENV:-development}`
  2019-08-20T12:46:04.051365+00:00 app[web.1]: Puma starting in single mode...
  2019-08-20T12:46:04.051387+00:00 app[web.1]: * Version 3.12.1 (ruby 2.6.1-p33), codename: Llamas in Pajamas
  2019-08-20T12:46:04.051389+00:00 app[web.1]: * Min threads: 5, max threads: 5
  2019-08-20T12:46:04.051390+00:00 app[web.1]: * Environment: production
  2019-08-20T12:46:08.886669+00:00 heroku[web.1]: State changed from starting to crashed
  2019-08-20T12:46:08.769945+00:00 app[web.1]: * Listening on tcp://0.0.0.0:32178
  2019-08-20T12:46:08.770225+00:00 app[web.1]: bundler: failed to load command: puma (/app/vendor/bundle/ruby/2.6.0/bin/puma)
  2019-08-20T12:46:08.770272+00:00 app[web.1]: Errno::ENOENT: No such file or directory @ rb_sysopen - tmp/pids/server.pid
  2019-08-20T12:46:08.770276+00:00 app[web.1]: /app/vendor/bundle/ruby/2.6.0/gems/puma-3.12.1/lib/puma/launcher.rb:133:in `initialize'
  2019-08-20T12:46:08.770277+00:00 app[web.1]: /app/vendor/bundle/ruby/2.6.0/gems/puma-3.12.1/lib/puma/launcher.rb:133:in `open'
  2019-08-20T12:46:08.770278+00:00 app[web.1]: /app/vendor/bundle/ruby/2.6.0/gems/puma-3.12.1/lib/puma/launcher.rb:133:in `write_pid'
  2019-08-20T12:46:08.770280+00:00 app[web.1]: /app/vendor/bundle/ruby/2.6.0/gems/puma-3.12.1/lib/puma/launcher.rb:106:in `write_state'
  2019-08-20T12:46:08.770281+00:00 app[web.1]: /app/vendor/bundle/ruby/2.6.0/gems/puma-3.12.1/lib/puma/single.rb:103:in `run'
  2019-08-20T12:46:08.770282+00:00 app[web.1]: /app/vendor/bundle/ruby/2.6.0/gems/puma-3.12.1/lib/puma/launcher.rb:186:in `run'
  2019-08-20T12:46:08.770284+00:00 app[web.1]: /app/vendor/bundle/ruby/2.6.0/gems/puma-3.12.1/lib/puma/cli.rb:80:in `run'
  2019-08-20T12:46:08.770285+00:00 app[web.1]: /app/vendor/bundle/ruby/2.6.0/gems/puma-3.12.1/bin/puma:10:in `&lt;top (required)&gt;'
  2019-08-20T12:46:08.770287+00:00 app[web.1]: /app/vendor/bundle/ruby/2.6.0/bin/puma:23:in `load'
  2019-08-20T12:46:08.770289+00:00 app[web.1]: /app/vendor/bundle/ruby/2.6.0/bin/puma:23:in `&lt;top (required)&gt;'
  2019-08-20T12:46:08.867275+00:00 heroku[web.1]: Process exited with status 1
  </code></pre>
  
  <p>For some reason, the <code>tmp/pids/server.pid</code> is not created when the server starts.</p>
  
  <p>Can you please help me with a solution to this problem?
  I did not find a solution in google</p>