Try running this:
sudo easy_install -U setuptools
In my case, this took me to setuptools version 25.4.0 for Python version 2.7 on my Mac, which I verified by running this:
sudo easy_install --version
setuptools 25.4.0 from /Library/Python/2.7/site-packages/setuptools-25.4.0-py2.7.egg (Python 2.7)