title: Gitlab dpl issue with ruby version
body: <p>I have a node app that I am deploying through Gitlab. I am using docker image <code>node:12.8.0</code>.</p>
  <p>Recently it has been failing deployment with the following error</p>
  <pre><code> $ dpl --provider=heroku --app=$HEROKU_DEVELOPMENT_APP --api-key=$HEROKU_API_KEY --skip-cleanup
   Installing deploy dependencies
   ERROR:  Error installing dpl-heroku:
       faraday requires Ruby version &gt;= 2.4.
   Successfully installed multipart-post-2.1.1
   Successfully installed ruby2_keywords-0.0.2
   /usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- dpl/provider/heroku (LoadError)
       from /usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
       from /var/lib/gems/2.3.0/gems/dpl-1.10.15/lib/dpl/provider.rb:93:in `rescue in block in new'
       from /var/lib/gems/2.3.0/gems/dpl-1.10.15/lib/dpl/provider.rb:68:in `block in new'
       from /var/lib/gems/2.3.0/gems/dpl-1.10.15/lib/dpl/cli.rb:41:in `fold'
       from /var/lib/gems/2.3.0/gems/dpl-1.10.15/lib/dpl/provider.rb:67:in `new'
       from /var/lib/gems/2.3.0/gems/dpl-1.10.15/lib/dpl/cli.rb:31:in `run'
       from /var/lib/gems/2.3.0/gems/dpl-1.10.15/lib/dpl/cli.rb:7:in `run'
       from /var/lib/gems/2.3.0/gems/dpl-1.10.15/bin/dpl:5:in `'
       from /usr/local/bin/dpl:22:in `load'
       from /usr/local/bin/dpl:22:in `'
   Running after_script
   00:01
   Running after script...
   $ echo &quot;Job - $CI_JOB_NAME ended.&quot;
   Job - deploy_development ended.
   Cleaning up file based variables
   00:01
   ERROR: Job failed: exit code 1
  </code></pre>
  <p>I am unable to install Ruby2.4 through <code>apt-get install ruby2.4</code>.</p>
  <p>Any advice would be appreciated.
  Thanks</p>