title: How to rescue from a require "gem_name" when the gem is not installed
body: <p>I'm writing a library that depend on a specific gem. I require the gem and use it in my code and everything is hunky-dory as long as the gem is installed on the user's machine. but what if it is not?!</p>
  
  <p>I thought it's fine cause I can rescue from the require command and print a message to the output to inform the user about the lacking gem and finish it gracefully but I get an error!</p>
  
  <p>Could you tell me how it should be done or what is wrong with this piece of code: </p>
  
  <pre><code>begin 
   require "some_gem"
  rescue
   puts "please install some_gem first!" 
  end
  </code></pre>