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- Issue 288, pull request 289: Add `six.assertNotRegex`.
- Issue 317: `six.moves._dummy_thread` now points to the `_thread` module on
Python 3.9+. Python 3.7 and later requires threading and deprecated the
`_dummy_thread` module.
- Issue 308, pull request 314: Remove support for Python 2.6 and Python 3.2.
- Issue 250, issue 165, pull request 251: `six.wraps` now ignores missing
attributes. This follows the Python 3.2+ standard library behavior.