title: ruby on rails - 1 error prohibited this listing from being saved: Image has contents that are not what they are reported to be
body: <p>1 error prohibited this listing from being saved:
  Image has contents that are not what they are reported to be</p>
  
  <p>That's the error that I get when I try to upload a picture for a listing. I've tried various types of validations and nothing is working.</p>
  
  <p>This is what my <strong>Model</strong> looks like.</p>
  
  <pre><code>class Listing &lt; ActiveRecord::Base
      has_attached_file :image, :styles =&gt; { :medium =&gt; "200x", :thumb =&gt;"100x100&gt;" }, :default_url =&gt; "default.jpg"
      validates_attachment :image, content_type: { content_type: /\Aimage\/.*\Z/ }
  end
  </code></pre>
  
  <p>Can someone please explain to me what I did wrong, and what I can do to fix it. I really want to keep working on this application but I've hit a problem!</p>