$ pip install --upgrade pip
Could not fetch URL https://pypi.python.org/simple/pip/: There was a problem confirming the ssl certificate: [SSL: TLSV1_ALERT_PROTOCOL_VERSION] tlsv1 alert protocol version (_ssl.c:645) - skipping
Requirement already up-to-date: pip in /Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages
$ pip --version
pip 9.0.1 from /Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages (python 3.5)
Upgrade pip using.
curl https://bootstrap.pypa.io/get-pip.py | python3
pip --version
pip 18.0 from /Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/pip (python 3.5)