title: Why is my excel add-in getting corrupted?
body: <p>I have a link to an excel add-in I let users download. I am using flask + mod_wsgi. </p>
  
  <pre><code>@app.route('/link/')
  def download_addin():
      parent_dir = os.path.dirname(os.path.dirname(os.path.realpath(__file__))) + '/static/'
  
      response = make_response()
      response.headers['Cache-Control'] = 'no-cache'
      response.headers['Content-Type'] = 'application/vnd.ms-excel.addin.macroEnabled.12'
      response.headers['Content-Disposition'] = 'attachment; filename=my_addin.xlam'
      return response
  </code></pre>
  
  <p>I download the file but when I use it in Excel I get a warning "Excel cannot open the file 'my_addin.xlam' because the file format or file extension is not valid...'</p>
  
  <p>Thanks!</p>