title: Issue importing netCF4 with python 3.9
body: <p>I'm trying to import netCDF4 and got this error message:</p>
  <pre><code>from netCDF4 import Dataset
  </code></pre>
  <blockquote>
  <p>from netCDF4 import *   File
  &quot;/home/username/.local/lib/python3.9/site-packages/netCDF4/<strong>init</strong>.py&quot;,
  line 3, in 
  from ._netCDF4 import * ModuleNotFoundError: No module named 'netCDF4._netCDF4'</p>
  </blockquote>
  <p>I did not have this issue before upgrading to python3.9. I can't find answer to this anywhere else. Thank you in advance.</p>