title: Pushing Rails to Heroku, can't find Rake taks
body: <p>UPDATE: now using Ruby 2.5.5  and Bundler 2.0.2, still getting the error: </p>
  
  <pre><code>/app/tmp/buildpacks/&lt;long hash&gt;/lib/language_pack/helpers/rake_runner.rb:106:
  in load_rake_tasks!': 
  Could not detect rake tasks (LanguagePack::Helpers::RakeRunner::CannotLoadRakefileError)` 
  </code></pre>
  
  <p>I'm trying to <code>git push heroku master</code> a Rails app for the first time, and I'm getting this error:</p>
  
  <pre><code>remote: -----&gt; Detecting rake tasks
  remote:
  remote: !
  remote: ! Could not detect rake tasks
  remote: ! ensure you can run `$ bundle exec rake -P` against your app
  remote: ! and using the production group of your Gemfile.
  remote: ! Activating bundler (2.0.1) failed:
  remote: ! Could not find 'bundler' (2.0.1) required by your /tmp/build_cf9981ccbdc1fd4f0b82703a5ff40ecc/Gemfile.lock.
  remote: ! To update to the latest version installed on your system, run `bundle update --bundler`.
  remote: ! To install the missing version, run `gem install bundler:2.0.1`
  remote: ! Checked in 'GEM_PATH=vendor/bundle/ruby/2.5.0', execute `gem env` for more information
  remote: !
  remote: ! To install the version of bundler this project requires, run `gem install bundler -v '2.0.1'`
  remote: !
  remote: /app/tmp/buildpacks/b7af5642714be4eddaa5f35e2b4c36176b839b4abcd9bfe57ee71c358d71152b4fd2cf925c5b6e6816adee359c4f0f966b663a7f8649b0729509d510091abc07/lib/language_pack/helpers/rake_runner.rb:106:in `load_rake_tasks!': Could not detect rake tasks (LanguagePack::Helpers::RakeRunner::CannotLoadRakefileError)
  remote: ensure you can run `$ bundle exec rake -P` against your app
  remote: and using the production group of your Gemfile.
  remote: Activating bundler (2.0.1) failed:
  remote: Could not find 'bundler' (2.0.1) required by your /tmp/build_cf9981ccbdc1fd4f0b82703a5ff40ecc/Gemfile.lock.
  remote: To update to the latest version installed on your system, run `bundle update --bundler`.
  remote: To install the missing version, run `gem install bundler:2.0.1`
  remote: Checked in 'GEM_PATH=vendor/bundle/ruby/2.5.0', execute `gem env` for more information
  remote:
  remote: To install the version of bundler this project requires, run `gem install bundler -v '2.0.1'`
  </code></pre>
  
  <p>I have run <code>gem install bundler:2.0.1</code> successfully in this app's root directory. My <code>$GEM_PATH</code> does not include <code>vendor/bundle/ruby/2</code>, and I don't know if altering it is the solution. If so, does that mean I need to alter it locally or remotely? If locally, is it done the same way as normal environment variables, or is there a special Rails setting I need to change?</p>
  
  <p>I have tried the suggestion in the accepted answer here:</p>
  
  <p><a href="https://stackoverflow.com/questions/36394297/heroku-push-error-could-not-detect-rake-tasks">heroku push error: &quot;Could not detect rake tasks&quot;</a></p>
  
  <p>but that made no difference. </p>
  
  <p>My problem also seems to be similar to the (unanswered) question here:</p>
  
  <p><a href="https://stackoverflow.com/questions/36322341/cant-push-rails-project-to-heroku">Can&#39;t Push Rails Project to Heroku</a></p>
  
  <p>Searching the Heroku Help Center didn't seem to yield any results, either.</p>
  
  <p>Any guidance about what I should do?</p>