title: Warning with fog and AWS: unable to load the 'unf' gem
body: <p>Every action in a rails console (rails server, rails console, db:migrate, etc.) raises a warning since my last bundle update:</p>
  
  <pre><code>[fog][WARNING] Unable to load the 'unf' gem. Your AWS strings may not be properly encoded.
  </code></pre>
  
  <p>I'm sure I didn't change anything in the AWS strings which are in my application.rb file:</p>
  
  <pre><code>    # Amazon S3 credentials
  ENV["AWS_ACCESS_KEY_ID"] = "AWS_ACCESS_KEY_ID"
  ENV["AWS_SECRET_ACCESS_KEY"] = "AWS_SECRET_ACCESS_KEY"
  ENV["AWS_S3_BUCKET"] = "my-bucket"
  </code></pre>
  
  <p>I don't have this "unf" gem in my gemfile. Should I add it?</p>