title: incompatible character encodings: UTF-8 and ASCII-8BIT in render action
body: <blockquote>
    <p>ActionView::Template::Error (incompatible character encodings: UTF-8
    and ASCII-8BIT):   app/controllers/posts_controller.rb:27:in `new'</p>
  </blockquote>
  
  <pre><code>  # GET /posts/new
    def new
      if params[:post]
        @post = Post.new(post_params).dup
        if @post.valid?
          render :action =&gt; "confirm"
        else
          format.html { render action: 'new' }
          format.json { render json: @post.errors, status: :unprocessable_entity }
        end
      else
        @post = Post.new
        @document = Document.new
        @documents = @post.documents.all
        @document = @post.documents.build
      end
  </code></pre>
  
  <p>I don't know why it is happening.</p>