This happens to me when I try to access resources in a native namespace package.

Tested on:

• Windows, Python 3.10.4
• Docker in WSL2, image python:3.10-slim, Python 3.10.5

The reason seems to be that importlib_resources.files() returns MultiplexedPath from stdlib (importlib.readers) rather than from importlib_resources.readers.

To recreate:

1. Install any namespace package, e.g. sphinxcontrib-htmlhelp;

   pip install sphinxcontrib-htmlhelp
   

2. Use files with joinpath to get the path of a resource.

   from importlib_resources import files
   
   print(root:=files('sphinxcontrib'), 'from', root.__module__)
   print(root.joinpath('htmlhelp', 'templates'))

Expected output (which I get with Pythons 3.7-3.9):

MultiplexedPath('/usr/local/lib/python3.9/site-packages/sphinxcontrib') from importlib_resources.readers
/usr/local/lib/python3.9/site-packages/sphinxcontrib/htmlhelp/templates

Bug with Pythons 3.10:

MultiplexedPath('/usr/local/lib/python3.10/site-packages/sphinxcontrib') from importlib.readers
Traceback (most recent call last):
  File "<string>", line 1, in <module>
TypeError: MultiplexedPath.joinpath() takes 2 positional arguments but 3 were given

I also tested with the code in #254 but to no aval.