sysconfig.get_path('platstdlib') return paths in virtual environments (or otherwise weird)

Bug report

The sysconfig.get_path function is supposed to return he following for its first argument:

• stdlib: directory containing the standard Python library files that are not platform-specific.
• platstdlib: directory containing the standard Python library files that are platform-specific.

E.g. in the python:3.11.1 Docker container:

>>> import sysconfig
>>> sysconfig.get_path('stdlib')
'/usr/local/lib/python3.11'
>>> sysconfig.get_path('platstdlib')
'/usr/local/lib/python3.11'

Or on a Python build configured with lib64 platlibdir (e.g. on Fedora Linux with $RPM_BUILD_ROOT environment variable set):

>>> import sysconfig
>>> sysconfig.get_path('stdlib')
'/usr/lib64/python3.11'
>>> sysconfig.get_path('platstdlib')
'/usr/lib64/python3.11'

Yet in virtual environments, the platstdlib directory returns a directory from within the virtual environment. E.g. in the python:3.11.1 Docker container:

>>> import sysconfig
>>> sysconfig.get_path('stdlib')
'/usr/local/lib/python3.11'
>>> sysconfig.get_path('platstdlib')
'.../myvenv/lib/python3.11'

Or on Fedora Linux:

>>> import sysconfig
>>> sysconfig.get_path('stdlib')
'/usr/lib64/python3.11'
>>> sysconfig.get_path('platstdlib')
'.../myvenv/lib64/python3.11'

This even confuses the default values on Fedora Linux (without $RPM_BUILD_ROOT environment variable set):

>>> import sysconfig
>>> sysconfig.get_path('stdlib')
'/usr/lib64/python3.11'
>>> sysconfig.get_path('platstdlib')
'/usr/local/lib64/python3.11'

I believe that here:

https://github.com/python/cpython/blob/62251c3da06eb4662502295697f39730565b1717/Lib/sysconfig.py#L30

The {platbase} variable should be replaced with {insatlled_base} or even (currently AFAIK nonexistent) {insatlled_platbase}.

Your environment

• CPython versions tested on: 3.11.1
• Operating system and architecture: Fedora Linux 37 x86_64, python:3.11.1 Docker container.

Comece em Lib/sysconfig.py, por volta da linha 30, e reproduza os resultados relatados de sysconfig.get_path('stdlib') e get_path('platstdlib') em um ambiente virtual, na imagem Docker Python 3.11.1 e no Fedora Linux. Considera-se concluído quando o caminho da biblioteca padrão específico da plataforma for consistente com a distinção documentada nesses ambientes, com cobertura de regressão adicionada onde a suíte de testes existente trata dos caminhos sysconfig.