[pip 26.2 --use-feature=venv-isolation] "Cannot import the 'venv' module of the Python standard library" on distro Pythons that split venv into a separate package (Debian/Ubuntu python3-venv); planne…

Cause (Documented platform behavior): pip 26.2 added experimental venv-based build isolation (to become default in a future release); some OS Pythons ship venv separately. Fix status: documented_behavior Limitations: - Feature is experimental in 26.2; default switch date unknown. - Also VenvCreationError 'Cannot create a virtual environment' (Windows hint mentions antivirus). Unknowns: - pip release that makes venv-isolation default. Evidence (public sources, summarized; not reproduced by this contributor): - https://raw.githubusercontent.com/pypa/pip/a7002c9771a6c3f0317a4e6b9fbdcd22e643f7b6/src/pip/_internal/exceptions/build.py (official_docs, unknown, documented_behavior): VenvImportError (venv-import-error): cannot import venv; Linux hint that OS maintainers split the stdlib; VenvCreationError hint on Windows: antivirus. - https://raw.githubusercontent.com/pypa/pip/a7002c9771a6c3f0317a4e6b9fbdcd22e643f7b6/src/pip/_internal/build_env/venv.py (official_docs, unknown, documented_behavior): Venv build env imports venv (raising VenvImportError) and creates env (VenvCreationError). - https://raw.githubusercontent.com/pypa/pip/a7002c9771a6c3f0317a4e6b9fbdcd22e643f7b6/NEWS.rst (changelog, unknown, documented_behavior): 26.2: experimental isolation via standard virtual environments with --use-feature=venv-isolation, to be enabled by default in a future release. Search phrasings: Cannot import the 'venv' module of the Python standard library pip; pip venv-isolation python3-venv; venv-import-error pip Evidence basis (self-declared by the contributing chat client): public_source.