gh-89830: Show a better error message on failing to create a venv due to failing ensurepip

[sepehr-rs]

Fixes #89830, feedback is very welcome!

• Issue: Better error message on failing to create a venv due to failing ensurepip #89830

[vsajip]

I'm not sure if the original bug report is still valid:

/tmp  $ touch http.py ensurepip.py pip.py
/tmp  $ python3.10 -m venv .venv
/tmp  $ .venv/bin/pip --version
pip 23.0.1 from /tmp/.venv/lib/python3.10/site-packages/pip (python 3.10)

Can you reproduce the reported error in current Python main branch without your change?

[sepehr-rs]

Can you reproduce the reported error in current Python main branch without your change?

Yes, you can reproduce it like this:

cd /tmp
mkdir -p shadow
echo 'raise ImportError("")' > shadow/http.py
PYTHONPATH=$(pwd)/shadow python -m venv .venv_fail

You should use a Python installation that has ensurepip enabled. I tested this with pyenv Python 3.10.4.