As far as I am aware, it is not currently supported. RobotPy is an independent project separate from WPILib, and they did not have the resources to take on porting for the VMX-Pi last I checked. I looked into running RobotPy on the VMX a bit ago, and quickly determined I did not know enough CPP(what they use for a backend) to port it myself. This was one of the reasons why our team began investigating switching to Java this past season (not just the VMX-Pi, but there are many devices, almost all I2C, not supported by robotpy directly).