problems importing obj from kenney.nl with colors/textures

[horstjens]

(see also posting in vpython mailing list https://groups.google.com/g/vpython-users/c/qokOrlyj2-c/m/Xtv4JJuUAgAJ )

The demo python script to import the spinning cubes into vpython works fine,
however when I try to import assets from kenney.nl (obj and mtl files) the program complains
( i try to import the "tree_small.obj" and "tree_small.mtl" files from https://www.kenney.nl/assets/city-kit-suburban )

ine 48, in obj_to_triangles
curtexture = str(material.texture._path)
^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute '_path'

After I changed the offending code line into:

if material.texture is not None: 
      curtexture = str(material.texture._path)

the import works, but I only get snow-white 3d objects, without any textures or colors.
How can I import obj and mtl files correctly so that i get a colored object in vpython?