Error in hdri_to_cubemap.py

[Almee98]

sky_box.set_shader(Shader.load(Shader.SLGLSL, 'shaders/skybox_v.glsl', 'shaders/skybox_f.glsl'), 1) TypeError: NodePath.set_shader() argument 1 must be Shader, not NoneType

[rdb]

That means the shader failed to load - what are the other error messages?