title: Rails translate custom base error
body: <p>My models:</p>
  
  <p>Product <code>has_many</code> variants <code>has_many</code> sizes</p>
  
  <p>To sizes I add custom error, like this:</p>
  
  <pre><code>errors.add :base, "My custom error msg"
  </code></pre>
  
  <p>In the view I see: "Sizes base My custom error msg"</p>
  
  <pre><code>class Size &lt; ActiveRecord::Base
    ...
    validate :custom_error, only: :update
    ...
    def custom_error
      errors.add :base, "My custom error msg"
    end
  end
  </code></pre>
  
  <p>But how translate this message?</p>
  
  <p><strong>UPDATED</strong> I am found solution:</p>
  
  <p>In locale.yml:</p>
  
  <pre><code>attributes:
    variants/sizes:
      base: ''
  </code></pre>