CI: Python 3.11 tests are failing because a dependency is using the deprecated 'sre_constants' module.

[WarrenWeckesser]

In recent pull requests, and for the most recent commit to the main development branch, the Python 3.11 tests are failing because some dependency is importing the deprecated Python module sre_constants:

============================= test session starts ==============================
platform linux -- Python 3.11.0b5, pytest-7.1.2, pluggy-1.0.0
rootdir: /home/runner/work/scipy/scipy, configfile: pytest.ini
plugins: timeout-2.1.0, forked-1.4.0, xdist-2.5.0
timeout: 60.0s
timeout method: signal
timeout func_only: False
collected 51360 items / 1 error / 12113 deselected / 39247 selected

==================================== ERRORS ====================================
_ ERROR collecting build/testenv/lib/python3.11/site-packages/scipy/_build_utils/tests/test_scipy_version.py _
/opt/hostedtoolcache/Python/3.11.0-beta.5/x64/lib/python3.11/importlib/__init__.py:126: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)

<snip>

        wkref      = <class 'weakref.ReferenceType'>
/opt/hostedtoolcache/Python/3.11.0-beta.5/x64/lib/python3.11/sre_constants.py:2: in <module>
    warnings.warn(f"module {__name__!r} is deprecated",
E   DeprecationWarning: module 'sre_constants' is deprecated
        __builtins__ = <builtins>
        __cached__ = '/opt/hostedtoolcache/Python/3.11.0-beta.5/x64/lib/python3.11/__pycache__/sre_constants.cpython-311.pyc'
        __doc__    = None
        __file__   = '/opt/hostedtoolcache/Python/3.11.0-beta.5/x64/lib/python3.11/sre_constants.py'
        __loader__ = <_frozen_importlib_external.SourceFileLoader object at 0x7f25ec586890>
        __name__   = 'sre_constants'
        __package__ = ''
        __spec__   = ModuleSpec(name='sre_constants', loader=<_frozen_importlib_external.SourceFileLoader object at 0x7f25ec586890>, origin='/opt/hostedtoolcache/Python/3.11.0-beta.5/x64/lib/python3.11/sre_constants.py')
        warnings   = <module 'warnings' from '/opt/hostedtoolcache/Python/3.11.0-beta.5/x64/lib/python3.11/warnings.py'>
=========================== short test summary info ============================
ERROR ../testenv/lib/python3.11/site-packages/scipy/_build_utils/tests/test_scipy_version.py
!!!!!!!!!!!!!!!!!!!! Interrupted: 1 error during collection !!!!!!!!!!!!!!!!!!!!
===================== 12113 deselected, 1 error in 14.81s ======================
Error: Process completed with exit code 1.

[WarrenWeckesser]

The problem might be in setuptools. When NumPy is installed, setuptools 59.8.0 is also installed:

...
  Created wheel for numpy: filename=numpy-1.24.0.dev0+573.g6e1557900-cp311-cp311-linux_x86_64.whl size=23096321 sha256=98a4bb2969082d927fd233cf3396d2b8aaca046f6b595b64f878b2dd74c32597
  Stored in directory: /tmp/pip-ephem-wheel-cache-b0au3z0w/wheels/bd/6b/e5/925e60986da27b602ad506d248e2a2888880fc1786c8e9ee3d
Successfully built numpy
Installing collected packages: numpy
Successfully installed numpy-1.24.0.dev0+573.g6e1557900
Collecting setuptools<60.0
  Downloading setuptools-59.8.0-py3-none-any.whl (952 kB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 952.8/952.8 kB 40.6 MB/s eta 0:00:00
...

setuptools issue 3274 is a report of the deprecation problem, and it refers to version 60.9.3, so version 59.8.0 still bundles a version of pyparsing that imports sre_constants.

The setuptools issue was fixed in pypa/setuptools#3276 (release note), which is part of version 62.3.0.

[rgommers]

These _bootstrap._gcd_import tracebacks are always clear as mud - I thought it may be the import re in test_scipy_version.py.

Either way, let me try to fix it by moving the job away from setuptools.