NameError: name 'UnsaturatedEngine' is not defined

Hi all,

This is kind of weird to me but does anyone else have this NameError like me?

NameError: name 'UnsaturatedEngine' is not defined

This error is come from:
"unsat=UnsaturatedEngine()"

I have also tried:
tpfe=TwoPhaseFlowEngine()

and I got the same
NameError: name 'TwoPhaseFlowEngine' is not defined

I still have file "UnsaturatedEngine.cpp" and "TwoPhaseFlowEngine.cpp" in my folder build/pkg/pfv

This happens when I reinstall Ubuntu 14.04.5 LTS (Trusty Tahr) and yade-1.20.0

However, when I tried:
fe=FlowEngine()
it got no error!

Before this installation, the above command "unsat=UnsaturatedEngine()" got no error and worked very fine.

Any idea about how to solve this would be greatly appreciated!

Thanks,

Son