title: pyexcel export error "No content, file name. Nothing is given"
body: <p>I'm using <code>django-pyexcel</code> to export data from the website, but when I go to the export URL I get the error:</p>
  <blockquote>
  <p>Exception Type: IOError</p>
  <p>Exception Value: No content, file name. Nothing is given</p>
  </blockquote>
  <p>The code to export the data was copied from the <a href="http://django-excel.readthedocs.io/en/latest/#handle-data-export" rel="noreferrer">example</a> given in the documentation:</p>
  <pre><code>return excel.make_response_from_a_table(Question, 'xls', file_name=&quot;sheet&quot;)
  </code></pre>