Python 3.12: ModuleNotFoundError: No module named 'setuptools'

[hugovk]

The Python 3.12 release candidate is out! 🚀

Call to action

We strongly encourage maintainers of third-party Python projects to prepare their projects for 3.12 compatibilities during this phase, and where necessary publish Python 3.12 wheels on PyPI to be ready for the final release of 3.12.0.

See also https://dev.to/hugovk/help-test-python-312-beta-1508/

Python 3.12.0 final will be released in one month: https://peps.python.org/pep-0693/

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However, when adding 3.12 to the CI like hugovk@427164b, it fails with:

―――――――――――――――――――――― TestInstallation.test_installation ――――――――――――――――――――――

self = <test.test_installation.TestInstallation testMethod=test_installation>
rw_dir = '/tmp/test_installationo1a7a3rg'

    @with_rw_directory
    def test_installation(self, rw_dir):
        self.setUp_venv(rw_dir)
        result = subprocess.run(
            [self.pip, "install", "-r", "requirements.txt"],
            stdout=subprocess.PIPE,
            cwd=self.sources,
        )
        self.assertEqual(
            0,
            result.returncode,
            msg=result.stderr or result.stdout or "Can't install requirements",
        )
        result = subprocess.run(
            [self.python, "setup.py", "install"],
            stdout=subprocess.PIPE,
            cwd=self.sources,
        )
>       self.assertEqual(
            0,
            result.returncode,
            msg=result.stderr or result.stdout or "Can't build - setup.py failed",
        )
E       AssertionError: 0 != 1 : Can't build - setup.py failed

test/test_installation.py:39: AssertionError
----------------------------- Captured stderr call -----------------------------
Traceback (most recent call last):
  File "/home/runner/work/GitPython/GitPython/setup.py", line 2, in <module>
    from setuptools import setup, find_packages
ModuleNotFoundError: No module named 'setuptools'

[EliahKagan]

This happens because, while the setuptools build backend remains supported including for projects like this one with setup.py files containing nontrivial logic, running setup.py directly is deprecated and, starting in Python 3.12, Python virtual (and global) environments no longer automatically have the setuptools package. See the ensurepip item in the list of removals in 3.12.

The test_installation test runs python setup.py install. The solution is to use pip install . instead, or pip install -e . when an editable install is desired (in test_installation, the README.md, and elsewhere).

I've opened #1654, which includes a fix for this issue.