python: create venv's --without-pip

[branchvincent]

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Currently, virtualenv_install_with_resources creates a venv with a full copy of pip. This is pretty wasteful, since we really only need it at build time to install resources. Instead, we can:

1. Create a venv using --without-pip
2. Use python@x.y's pip to install resources into this venv, using the --python option
3. Tangentially, remove all shell activate scripts (which admittedly doesn't save much but aren't necessary)

As a result, this saves ~7MB of disk space per venv:

$ brew install black
...
==> Summary
🍺  /opt/homebrew/Cellar/black/23.7.0_1: 1,121 files, 13.5MB
$ brew reinstall -s black
...
==> Summary
🍺  /opt/homebrew/Cellar/black/23.7.0_1: 558 files, 6.6MB, built in 41 seconds

Note I don't foresee this causing any issues, but I've left an opt-out to be safe.

[MikeMcQuaid]

Makes sense to me! Could you add a commented-out odeprecated for the opt-out so we can remove it if it's unused? Thanks!

[branchvincent]

Done!

[MikeMcQuaid]

Thanks again @branchvincent!

[cangussu]

I have a bunch of machines running different brew versions and a formula that uses virtualenv_create and relies on the fact that pip is available. What is the proper way to deal with this change? It broke my formula with new version of brew but if I add the extra parameter it will break on older versions.

[branchvincent]

Sorry about that!

running different brew versions

may be a silly question, but is updating to the latest version not an option?

relies on the fact that pip is available

in what way? there may be a simple change you could make, like Homebrew/homebrew-core#138661 (comment)

[MikeMcQuaid]

I have a bunch of machines running different brew versions and a formula that uses virtualenv_create and relies on the fact that pip is available.

@cangussu Which versions? Note we do not support running any Homebrew versions beyond the latest.

[bebound]

This also removes setuptools. Some namespace packages may rely on it:

linuxbrew@794b47da48b2:/down$ az -v
Traceback (most recent call last):
  File "/home/linuxbrew/.linuxbrew/opt/python@3.10/lib/python3.10/runpy.py", line 187, in _run_module_as_main
    mod_name, mod_spec, code = _get_module_details(mod_name, _Error)
  File "/home/linuxbrew/.linuxbrew/opt/python@3.10/lib/python3.10/runpy.py", line 110, in _get_module_details
    __import__(pkg_name)
  File "/home/linuxbrew/.linuxbrew/Cellar/azure-cli/2.51.0/libexec/lib/python3.10/site-packages/azure/__init__.py", line 1, in <module>
    __import__('pkg_resources').declare_namespace(__name__)
ModuleNotFoundError: No module named 'pkg_resources'

[branchvincent]

Since setuptools is included with our python, you'll only run into trouble if you've disabled system_site_packages

Also note if you use setuptools at runtime, you really should add it to your requirements as Python 3.12 will no longer include it either python/cpython#95299 pypa/pip#12032

[cangussu]

@branchvincent I followed your suggestion to use python -m pip and it worked for our use case, tks!

in what way? there may be a simple change you could make, like Homebrew/homebrew-core#138661 (comment)