Unable to activate sinatra-1.4.7, because rack-2.0.1 conflicts with rack (~> 1.5)
<p>I Just updated my OS from Ubuntu 14.04 LTS to 16.04, and I was running my Ruby Sinatra project in there. The thing is after the update I tried to ran The server and then localhost in browser I got this error
    Boot Error</p>

<pre><code>Something went wrong while loading app.rb
Gem::ConflictError: Unable to activate sinatra-1.4.7, because rack-2.0.1 conflicts with rack (~&gt; 1.5)

/usr/lib/ruby/2.3.0/rubygems/specification.rb:2286:in `raise_if_conflicts'
/usr/lib/ruby/2.3.0/rubygems/specification.rb:1407:in `activate'
/usr/lib/ruby/2.3.0/rubygems.rb:196:in `rescue in try_activate'
/usr/lib/ruby/2.3.0/rubygems.rb:193:in `try_activate'
/usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:125:in `rescue in require'
/usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:40:in `require'
/home/leandro/Downloads/git-master/ruby sinatra/app.rb:1:in `&lt;top (required)&gt;'
/usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
/usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
/var/lib/gems/2.3.0/gems/shotgun-0.9.1/lib/shotgun/loader.rb:115:in `inner_app'
/var/lib/gems/2.3.0/gems/shotgun-0.9.1/lib/shotgun/loader.rb:103:in `assemble_app'
/var/lib/gems/2.3.0/gems/shotgun-0.9.1/lib/shotgun/loader.rb:86:in `proceed_as_child'
/var/lib/gems/2.3.0/gems/shotgun-0.9.1/lib/shotgun/loader.rb:31:in `call!'
/var/lib/gems/2.3.0/gems/shotgun-0.9.1/lib/shotgun/loader.rb:18:in `call'
/var/lib/gems/2.3.0/gems/shotgun-0.9.1/lib/shotgun/favicon.rb:12:in `call'
/var/lib/gems/2.3.0/gems/shotgun-0.9.1/lib/shotgun/static.rb:14:in `call'
/var/lib/gems/2.3.0/gems/rack-2.0.1/lib/rack/urlmap.rb:68:in `block in call'
/var/lib/gems/2.3.0/gems/rack-2.0.1/lib/rack/urlmap.rb:53:in `each'
/var/lib/gems/2.3.0/gems/rack-2.0.1/lib/rack/urlmap.rb:53:in `call'
/var/lib/gems/2.3.0/gems/rack-2.0.1/lib/rack/builder.rb:153:in `call'
/var/lib/gems/2.3.0/gems/rack-2.0.1/lib/rack/handler/webrick.rb:86:in `service'
/usr/lib/ruby/2.3.0/webrick/httpserver.rb:140:in `service'
/usr/lib/ruby/2.3.0/webrick/httpserver.rb:96:in `run'
/usr/lib/ruby/2.3.0/webrick/server.rb:296:in `block in start_thread'
</code></pre>

<p>I already tried gem install bundle and bundle install inside the folder that contains app.rb. I also put gem "rack", "~> 1.5" in the gem file but I still have the same error. Can you please help me? thanks a lot in advance</p>