Segmentation Fault when calling render()

[almajo]

I spent some time looking for a fix for a segmentation fault when calling env.render() for any roboschool environment.

Source of the fault was the missing apt-get install libgl1-mesa-dev as stated in the installation section.

However, there it says it is only necessary on a headless machine, while I am running a classic Ubuntu 18.04 computer.

The fault is thrown when accessing scene.cpp_world in gym_mujoco_xml_env.py

It would be nice to 1.) have the installation prerequisite saying that libgl1-mesa could also be needed in a normal machine. 2.) validating that the needed cpp code is accessible because a segmentation fault is not the nicest stacktrace