You’re still installing version 3.6, not the current master branch which is the unfinished version 3.7. To install that you need to
pip3 uninstall pymc3
pip3 install git+https://github.com/pymc-devs/pymc3.git
You’re still installing version 3.6, not the current master branch which is the unfinished version 3.7. To install that you need to
pip3 uninstall pymc3
pip3 install git+https://github.com/pymc-devs/pymc3.git