title: Rails commands in home directory result in "i18n gem is not available" error
body: <p>I was in my Ubuntu home directory, trying to create a new rails app with <code>rails new</code>, but I got this error:</p>
  
  <blockquote>
    <p>The i18n gem is not available. Please add it to your Gemfile and run bundle install</p>
  </blockquote>
  
  <p>Any rails command I run gives that error. I'm really confused, because I'm not inside an application. I'm just in my home directory. There is no gemfile. I tried installing 'i18n' into my home directory with <code>gem install 'i18n'</code>, and it worked, but I'm still getting that error.</p>
  
  <p>I've never had any problems with rails commands in my home directory before. Everything rails-related works normally when I <code>cd</code> into my individual apps. What's going on?</p>
  
  <p><strong>Also</strong>, I'm now getting the same error in all my existing rails apps. Did rails suddenly become reliant on that gem? Or could deleting the gem in my home directory somehow have made it unavailable in my apps?</p>
  
  <hr>
  
  <h2>UPDATE</h2>
  
  <p>I tried <code>gem cleanup rails</code> and reinstalling, but nothing changed. Here was the result:</p>
  
  <pre><code>$ gem cleanup rails
    Cleaning up installed gems...
    Attempting to uninstall rails-4.0.10
    Successfully uninstalled rails-4.0.10
    Attempting to uninstall rails-4.2.1
    Successfully uninstalled rails-4.2.1
    Attempting to uninstall rails-4.2.4
    Successfully uninstalled rails-4.2.4
    Attempting to uninstall rails-5.0.1
    Successfully uninstalled rails-5.0.1
    Attempting to uninstall rails-5.0.2
    Successfully uninstalled rails-5.0.2
    Attempting to uninstall rails-5.0.3
    Successfully uninstalled rails-5.0.3
    Attempting to uninstall rails-5.0.4
    Successfully uninstalled rails-5.0.4
    Clean Up Complete
  $ gem install rails -v 5.0.1
    Fetching: rails-5.0.1.gem (100%)
    Successfully installed rails-5.0.1
    Parsing documentation for rails-5.0.1
    Installing ri documentation for rails-5.0.1
    Done installing documentation for rails after 1 seconds
    1 gem installed
  $ rails -v
    The i18n gem is not available. Please add it to your Gemfile and run bundle install
  </code></pre>
  
  <hr>
  
  <h2>UPDATE 2</h2>
  
  <p>I had previously manually installed <code>i18n</code> and I thought that might be the problem so I uninstalled both <code>rails</code> and <code>i18n</code> and reinstalled <code>rails</code>. But I'm still getting the error:</p>
  
  <pre><code>  $ gem uninstall rails --all
  
  You have requested to uninstall the gem:
      rails-5.0.1
  
  browser-2.3.0 depends on rails (&gt;= 0, development)
  browser-1.1.0 depends on rails (&gt;= 0, development)
  browser-0.9.1 depends on rails (&gt;= 0, development)
  carrierwave-1.2.1 depends on rails (&gt;= 4.0.0, development)
  carrierwave-1.0.0 depends on rails (&gt;= 4.0.0, development)
  rails_serve_static_assets-0.0.5 depends on rails (&gt;= 3.1, development)
  rails_serve_static_assets-0.0.4 depends on rails (&gt;= 3.1, development)
  sass-rails-4.0.5 depends on rails (&gt;= 0, development)
  sunspot_rails-2.2.7 depends on rails (&gt;= 3)
  twitter-typeahead-rails-0.10.5 depends on rails (&gt;= 3.1, development)
  yaml_db_improved-1.0.1 depends on rails (&gt;= 0)
  If you remove this gem, these dependencies will not be met.
  Continue with Uninstall? [yN]  y
  Successfully uninstalled rails-5.0.1
  
    $ gem uninstall i18n --all
  
  You have requested to uninstall the gem:
      i18n-0.9.1
  
  activesupport-5.1.4 depends on i18n (~&gt; 0.7)
  activesupport-5.0.5 depends on i18n (~&gt; 0.7)
  activesupport-5.0.4 depends on i18n (~&gt; 0.7)
  activesupport-5.0.3 depends on i18n (~&gt; 0.7)
  activesupport-5.0.2 depends on i18n (~&gt; 0.7)
  activesupport-5.0.1 depends on i18n (~&gt; 0.7)
  activesupport-4.2.4 depends on i18n (~&gt; 0.7)
  activesupport-4.2.1 depends on i18n (~&gt; 0.7)
  activesupport-4.0.10 depends on i18n (&gt;= 0.6.9, ~&gt; 0.6)
  capistrano-3.8.0 depends on i18n (&gt;= 0)
  capistrano-3.7.2 depends on i18n (&gt;= 0)
  If you remove this gem, these dependencies will not be met.
  Continue with Uninstall? [yN]  y
  Successfully uninstalled i18n-0.9.1
  
    $ gem install rails --version 5.0.1
  
  Fetching: i18n-0.9.1.gem (100%)
  Successfully installed i18n-0.9.1
  Fetching: rails-5.0.1.gem (100%)
  Successfully installed rails-5.0.1
  Parsing documentation for i18n-0.9.1
  Installing ri documentation for i18n-0.9.1
  Parsing documentation for rails-5.0.1
  Installing ri documentation for rails-5.0.1
  Done installing documentation for i18n, rails after 4 seconds
  2 gems installed
  
    $ rails -v
  
  The i18n gem is not available. Please add it to your Gemfile and run bundle install
  /home/user/.rvm/rubies/ruby-2.3.3/lib/ruby/site_ruby/2.3.0/rubygems/specification.rb:2278:in `check_version_conflict': can't activate activesupport-5.1.4, alrea
  ...
  </code></pre>