Summarized Changelog:

• get_requires_for_build_sdist hook is assumed to return an empty list if left unimplemented by the backend build system
• --devenv no longer modifies the directory in which the .tox environment is provisioned
• Fix show config when the package names are not in canonical form
• Fix a tox-conda isolation build bug
• tox can now be invoked with a new --no-provision flag that prevents provision
• Added Unicode support in pyproject.toml

Full changelogs available here.

Depends on D11687 and D11691

Part of T9866

Thanks to @algent for figuring out the tests.

Builds and works with both older py and updated py.

Run this version of tox on its own source code for both Python 2.7 and 3.9.