afni.nimh.nih.gov

Besides Peter's suggestion, you could brew install the needed libraries or configure python with a custom path. See link below. I don't have the El Capitan OS myself, so I can't try it out. Post your success/failure.

http://apple.stackexchange.com/questions/209572/how-to-use-pip-after-the-el-capitan-max-os-x-upgrade