Remove bundled setuptools

[sbidoul]

Feature or enhancement

Remove the bundled setuptools so that ensurepip and python -m venv only installs pip.

Context

The setup.py install command of setuptools is deprecated.

However, in an environment where setuptools is installed but wheel is not (such as one created with python -m venv), pip falls back on running the deprecated and non-standard setup.py install.

Since version 22.1 pip works correctly by default in environments where setuptools is not installed, by enabling its PEP 517 mode automatically, leading to unsurprising installations in most cases.

So, in order to progressively expose more users to standard-based installation workflows, we (the pip team) would like that virtual environments are created without setuptools by default.

Users faced with failing installations following this change (likely due to packages with customized setup.py that do not support building a wheel) can easily pip install setuptools to solve the issue.

Previous discussion

pypa/pip#8102 (comment) and following comments has some more context.

Linked PRs

• gh-95299: Stop installing setuptools as a part of ensurepip and venv #101039
• gh-95299: Rework test_cppext.py to not invoke setup.py directly #103316
• gh-95299: Remove lingering setuptools reference in installer scripts #103613

[sbidoul]

@pablogsal do you think it is still acceptable to do this in 3.11? If positive we can likely land a PR on time for RC1.

[pablogsal]

Unfortunately I don't feel comfortable landing this so late in the release cycle, specially so close to RC1 and given the current stability of 3.11 :(

This will need to wait until 3.12.

[rafrafek]

It feels strange that setuptools is included when using -m venv, but wheel is not included.

[pradyunsg]

I've filed #101039 for this (almost had a number with three 0s), targetting 3.12.

[edmorley]

Since version 22.1 pip works correctly by default in environments where setuptools is not installed, by enabling its PEP 517 mode automatically, leading to unsurprising installations in most cases.

Do you have some examples of cases where the PEP 517 mode doesn't work for legacy packages? :-)

[FFY00]

PEP 517 is backwards compatible, it should work on legacy packages, the opposite is the issue, pip trying to use the legacy path for packages that need PEP 517.