title: undefined method `path' with csv import via sidekiq
body: <p>I am trying to import a large csv via <code>sidekiq</code>. But i am facing problem.</p>
  
  <p>I wrote <code>import</code> method in my controller.</p>
  
  <pre><code>  def import
     Importcsv.perform_async(params[:file])
     redirect_to calendars_path, notice: "Calendar imported."
    end
  </code></pre>
  
  <p>And Worker code is here.</p>
  
  <pre><code>class Importcsv
    include Sidekiq::Worker
    sidekiq_options queue: "high"
  
   def perform(file)
     CSV.foreach(file.path, headers: true) do |row|
     calendar = find_by_id(row['id']) || new
       calendar.attributes = row.to_hash
       calendar.save
     end
   end
  end
  </code></pre>
  
  <p>But i got this error <code>undefined method</code>path' for "/tmp/RackMultipart20150928-8812-sgwsm5":String`</p>