title: How to fix "Could not install packages due to an EnvironmentError: HTTPSConnectionPool" error?
body: <p><strong>I'm trying to install jupyterthemes package and getting this error.</strong></p>
  
  <p><img src="https://i.stack.imgur.com/99OvX.jpg" alt="enter image description here"></p>
  
  <pre><code>Collecting jupyterthemes
    Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProtocolError('Connection aborted.', ConnectionResetError(10054, 'An existing connection was forcibly closed by the remote host', None, 10054, None))': /packages/8a/08/9dee6dfd7f2aad6c30282d55c8f495b4dc1e4747b4e2bdbeb80572ddf312/jupyterthemes-0.20.0-py2.py3-none-any.whl
    Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProtocolError('Connection aborted.', ConnectionResetError(10054, 'An existing connection was forcibly closed by the remote host', None, 10054, None))': /packages/8a/08/9dee6dfd7f2aad6c30282d55c8f495b4dc1e4747b4e2bdbeb80572ddf312/jupyterthemes-0.20.0-py2.py3-none-any.whl
    Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProtocolError('Connection aborted.', ConnectionResetError(10054, 'An existing connection was forcibly closed by the remote host', None, 10054, None))': /packages/8a/08/9dee6dfd7f2aad6c30282d55c8f495b4dc1e4747b4e2bdbeb80572ddf312/jupyterthemes-0.20.0-py2.py3-none-any.whl
    Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProtocolError('Connection aborted.', ConnectionResetError(10054, 'An existing connection was forcibly closed by the remote host', None, 10054, None))': /packages/8a/08/9dee6dfd7f2aad6c30282d55c8f495b4dc1e4747b4e2bdbeb80572ddf312/jupyterthemes-0.20.0-py2.py3-none-any.whl
    Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProtocolError('Connection aborted.', ConnectionResetError(10054, 'An existing connection was forcibly closed by the remote host', None, 10054, None))': /packages/8a/08/9dee6dfd7f2aad6c30282d55c8f495b4dc1e4747b4e2bdbeb80572ddf312/jupyterthemes-0.20.0-py2.py3-none-any.whl
  Could not install packages due to an EnvironmentError: HTTPSConnectionPool(host='files.pythonhosted.org', port=443): Max retries exceeded with url: /packages/8a/08/9dee6dfd7f2aad6c30282d55c8f495b4dc1e4747b4e2bdbeb80572ddf312/jupyterthemes-0.20.0-py2.py3-none-any.whl (Caused by ProtocolError('Connection aborted.', ConnectionResetError(10054, 'An existing connection was forcibly closed by the remote host', None, 10054, None)))
  </code></pre>