Check whether the interpreter currently set in PATH is associated with a virtual environment #4009
Description
This issue is forked from #3951.
When I attempt to use uv in a pyenv-virtualenv, I receive an error message indicating that there are no Python interpreters found in virtual environments. Since sys.prefix!=sys.base_prefix within a pyenv-virtualenv, it would be nice to be able to use uv therein, without having to invoke with --python=$(which python).
$ venv_name=uv
$ pyenv uninstall --force ${venv_name}
$ pyenv virtualenv ${venv_name}
$ pyenv shell ${venv_name}
$ pip install uv
[details omitted]
$ uv --version
uv 0.2.6 (a589ad506 2024-06-03)
$ pyenv version
uv (set by PYENV_VERSION environment variable)
$ python -c 'import sys; print(f"{(sys.prefix==sys.base_prefix)=}")'
(sys.prefix==sys.base_prefix)=False
$ uv pip install --upgrade pip --verbose
DEBUG Searching for Python interpreter in virtual environments
error: No Python interpreters found in virtual environments