pyversion can't be set in startup file on Linux

I am running R2017b on Ubuntu 16.04 LTS. I would like to make sure that while working on a particular project I always have python loaded. So I tried to put a python call in the startup.m file (or use the pyversion command) to make sure that python was loaded.

But Matlab errors and can't find the "py" variable, and subsequently can't finish the startup file. Yet, if I run the startup file just after Matlab is opened, it works just fine.

How can I make sure that python is loaded in my startup file? Or does Matlab only load its python interface after the call to startup.m?