from urllib.request import urlretrieve
url = "https://www.cs.cmu.edu/~./enron/enron_mail_20150507.tgz"
urlretrieve(url, filename="../enron_mail_20150507.tgz")

/Applications/Python 3.6/Install Certificates.command

-- pip install --upgrade certifi
Collecting certifi
  Using cached https://files.pythonhosted.org/packages/56/9d/1d02dd80bc4cd955f98980f28c5ee2200e1209292d5f9e9cc8d030d18655/certifi-2018.10.15-py2.py3-none-any.whl
Installing collected packages: certifi
  Found existing installation: certifi 2018.4.16
    Uninstalling certifi-2018.4.16:
Could not install packages due to an EnvironmentError: [Errno 13] Permission denied: '/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/certifi-2018.4.16.dist-info/DESCRIPTION.rst'
Consider using the `--user` option or check the permissions.

pip install --upgrade certifi