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- Drop Python 2.7, 3.4, 3.5, 3.6.
- Add support for Python 3.9, 3.10, 3.11, 3.12.
- No longer expect ``pkg_resources`` to be available in the created virtualenv.
- No longer depend on ``setuptools``.
- Add ``extra_args`` to ``install()`` and ``create()`` to pass extra arguments
to the underlying commands.
- Add ``raises=False`` option to ``get_version()`` to avoid raising an
exception if a package is not installed.