[SCons] Fix running the Python 3 test suite
[SCons] Fix running the Python 3 test suite

imitrichev/cantera,imitrichev/cantera,imitrichev/cantera,imitrichev/cantera,imitrichev/cantera,Heathckliff/cantera,Heathckliff/cantera,imitrichev/cantera,Heathckliff/cantera,Heathckliff/cantera,Heathckliff/cantera,Heathckliff/cantera