python3-light: cannot import importlib.metadata

Maintainer: @jefferyto
Environment: x86 / 22.03, x86 / master

Description: python3-light installs importlib.metadata package, that can't be imported

$ docker run --rm  -it openwrtorg/rootfs:x86-64
[...]
root@container:/# opkg update
root@container:/# opkg install python3-light
root@container:/# ls /usr/lib/python3.10/importlib/metadata/
__init__.pyc      _adapters.pyc     _collections.pyc  _functools.pyc    _itertools.pyc    _meta.pyc         _text.pyc
root@container:/# python3 -c "import importlib.metadata"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python3.10/importlib/metadata/__init__.py", line 6, in <module>
ModuleNotFoundError: No module named 'email'

discovered by : https://github.com/openwrt/packages/issues/20441

It seems it requires at least python3-email and python3-urllib

root@container:/# opkg install python3-email
Installing python3-email (3.10.7-3) to root...
Downloading https://downloads.openwrt.org/snapshots/packages/x86_64/packages/python3-email_3.10.7-3_x86_64.ipk
Configuring python3-email.
root@container:/# python3 -c "import importlib.metadata"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python3.10/importlib/metadata/__init__.py", line 7, in <module>
  File "/usr/lib/python3.10/pathlib.py", line 14, in <module>
ModuleNotFoundError: No module named 'urllib'
root@container:/# opkg install python3-urllib
Installing python3-urllib (3.10.7-3) to root...
Downloading https://downloads.openwrt.org/snapshots/packages/x86_64/packages/python3-urllib_3.10.7-3_x86_64.ipk
Configuring python3-urllib.
root@container:/# python3 -c "import importlib.metadata"
root@container:/# 

Also found https://github.com/openwrt/packages/issues/12942 by looking around in the issue tracker

Locate the python3-light package definition and inspect how its runtime dependencies are declared. Reproduce the issue with python3 -c "import importlib.metadata" in the shown OpenWrt image, then verify the import succeeds after installing the package with its required dependencies.