Blender removed the "Keep Custom Normals" checkbox on the Triangulate Modifier in 4.2, and that is now the default behavior. This causes exports with SourceOps to fail, since from what I can tell it ...
bpy.ops.wm.addon_disable('EXEC_SCREEN',module="io_scene_valvesource") bpy.ops.wm.addon_disable('EXEC_SCREEN',module="io_smd_tools") bpy.ops.wm.addon_enable('EXEC ...