title: cannot import workbook in openpyxl
body: <p>I have installed openpyxl in ubuntu.<br>
  now I am running the openpyxl with xlsx files.</p>
  
  <p>While importing the module, it gives me the following error.</p>
  
  <pre><code>from openpyxl import Workbook
  ImportError: cannot import name Workbook
  </code></pre>
  
  <p>Can anyone knows what I have to do to solve the problem?</p>