After install soya3, when plot elements, it still says `Soya3D not available'.

[Yang Zongze]

Recently, I download the latest docker image (fenicsproject/stable:latest). I found the soya is not install, so I intalled soya3. However, the warning still says that "Unable to plot element, Soya3D not available (install package python-soya)." Then I checked the code, and find the following code in ffc/plot.py. It import soya package by soya, but I think it shoud be soya3. Is it right?

# Import Soya3D
try:
    import soya
    from soya.sphere import Sphere
    from soya.label3d import Label3D
    from soya.sdlconst import QUIT
    _soya_imported = True
except ImportError:
    _soya_imported = False