[ci] [python-package] Python 3.8 jobs failing importing pyparsing: TypeError: 'type' object is not subscriptable

[jameslamb]

Description

Python 3.8 CI jobs are failing at test-collection time with the following error:

E TypeError: 'type' object is not subscriptable

full trace (click me)

_________ ERROR collecting tests/python_package_test/test_utilities.py _________
tests/python_package_test/test_utilities.py:7: in <module>
    import lightgbm as lgb
../../../miniforge/envs/test-env/lib/python3.8/site-packages/lightgbm/__init__.py:11: in <module>
    from .basic import Booster, Dataset, Sequence, register_logger
../../../miniforge/envs/test-env/lib/python3.8/site-packages/lightgbm/basic.py:29: in <module>
    from .compat import (
../../../miniforge/envs/test-env/lib/python3.8/site-packages/lightgbm/compat.py:191: in <module>
    import matplotlib  # noqa: F401
../../../miniforge/envs/test-env/lib/python3.8/site-packages/matplotlib/__init__.py:129: in <module>
    from . import _api, _version, cbook, _docstring, rcsetup
../../../miniforge/envs/test-env/lib/python3.8/site-packages/matplotlib/rcsetup.py:28: in <module>
    from matplotlib._fontconfig_pattern import parse_fontconfig_pattern
../../../miniforge/envs/test-env/lib/python3.8/site-packages/matplotlib/_fontconfig_pattern.py:15: in <module>
    from pyparsing import (
../../../miniforge/envs/test-env/lib/python3.8/site-packages/pyparsing/__init__.py:129: in <module>
    from .util import *
../../../miniforge/envs/test-env/lib/python3.8/site-packages/pyparsing/util.py:14: in <module>
    class __config_flags:
../../../miniforge/envs/test-env/lib/python3.8/site-packages/pyparsing/util.py:17: in __config_flags
    _all_names: list[str] = []
E   TypeError: 'type' object is not subscriptable

Reproducible example

This is happening on master and multiple PRs, for example: https://github.com/microsoft/LightGBM/actions/runs/11319863184/job/31476544070?pr=6679

Environment info

N/A

Additional Comments

The stacktrace points to pyparsing, which recently did a 3.2.0 release

pyparsing-3.2.0            |     pyhd8ed1ab_0          90 KB  conda-forge

In those release notes (link), it says

Discontinued support for Python 3.6, 3.7, and 3.8

The package metadata was updated to python-requires >=3.9 in package metadata and source code there (code link), but not in the conda-forge recipe (code link).

Similar to these:

• zipp: [ci] Python 3.7 CI jobs broken by zipp release #5969
• python-graphviz: bump to python >=3.8 conda-forge/python-graphviz-feedstock#56 and [ci] put ceiling on graphviz in Python 3.7 jobs #6370