title: Paperclip model validation error message appears two times
body: <p>I have upload funtionality in rails, am using rails paper clip. I have defined my model validation like this to check image type. </p>
  
  <p><code>validates_attachment :company_logo, content_type: { content_type: ["image/jpg", "image/jpeg", "image/png", "image/gif"] }</code> </p>
  
  <p>If i upload some other file extensions, its showing two times this message. I want only one message <code>"Company logo content type is invalid"</code></p>
  
  <pre><code>Company logo content type is invalid
  Company logo is invalid
  </code></pre>
  
  <p>Please tell me solution. Thanks in advance</p>