Log Message:
py-contextlib2: updated to 21.6.0

21.6.0 (2021-06-27)

* License update: due to the inclusion of type hints from the ``typeshed``
  project, the ``contextlib2`` project is now under a combination of the
  Python Software License (existing license) and the Apache License 2.0
  (``typeshed`` license)
* Switched to calendar based versioning using a \ 
"year"-"month"-"serial" scheme,
  rather than continuing with pre-1.0 semantic versioning
* Due to the inclusion of asynchronous features from Python 3.7+, the
  minimum supported Python version is now Python 3.6
* Synchronised with the Python 3.10 version of contextlib
  following new features available on Python 3.6+:

  * ``asyncontextmanager`` (added in Python 3.7, enhanced in Python 3.10)
  * ``aclosing`` (added in Python 3.10)
  * ``AbstractAsyncContextManager`` (added in Python 3.7)
  * ``AsyncContextDecorator`` (added in Python 3.10)
  * ``AsyncExitStack`` (added in Python 3.7)
  * async support in ``nullcontext`` (Python 3.10)

* ``contextlib2`` now includes an adapted copy of the ``contextlib``
  type hints from ``typeshed`` (the adaptation removes the Python version
  dependencies from the API definition)
* to incorporate the type hints stub file and the ``py.typed`` marker file,
  ``contextlib2`` is now installed as a package rather than as a module
* Updates to the default compatibility testing matrix:

  * Added: CPython 3.9, CPython 3.10
  * Dropped: CPython 2.7, CPython 3.5, PyPy2