title: Rails 5 break validating chain when a validation failed
body: <p>In my user model I have a validation rule like:</p>
  
  <pre><code>validates :email, presence: true, my_email_format: true, uniqueness: true
  </code></pre>
  
  <p>I want to break the chain when any validation is failed, such as when the email format is wrong (my_email_format failed), the uniqueness validation will not run.</p>