When I try to do a pip install Flask I get some ssl errors. If I try to add exceptions there is no difference. I googled around and see some discussion on this from a year ago but nothing else (see https://github.com/pypa/pip/issues/5063)
(venv) pip install -U flask --trusted-host=pypi.python.org --trusted-host=pypi.org --trusted-host=files.pythonhosted.org
Collecting flask
Could not fetch URL https://pypi.python.org/simple/flask/: There was a problem confirming
the ssl certificate: [SSL: TLSV1_ALERT_PROTOCOL_VERSION] tlsv1 alert protocol version (_ssl.c:590) - skipping
Could not find a version that satisfies the requirement flask (from versions: )
No matching distribution found for flask