contextlib2 21.6.0

Updating to a new stdlib reference version

As of Python 3.10, 4 files needed to be copied from the CPython reference implementation to contextlib2:

• Doc/contextlib.rst -> docs/contextlib2.rst

• Lib/contextlib.py -> contextlib2/__init__.py

• Lib/test/test_contextlib.py -> test/test_contextlib.py

• Lib/test/test_contextlib_async.py -> test/test_contextlib_async.py

The corresponding version of contextlib2/__init__.pyi also needs to be retrieved from the typeshed project:

wget https://raw.githubusercontent.com/python/typeshed/master/stdlib/contextlib.pyi

For the 3.10 sync, the only changes needed to the test files were to import from contextlib2 rather than contextlib. The test directory is laid out so that the test suite’s imports from test.support work the same way they do in the main CPython test suite.

The following patch files are saved in the dev directory:

• changes made to contextlib2/__init__.py to get it to run on the older versions (and to add back in the deprecated APIs that never graduated to the standard library version)

• changes made to contextlib2/__init__.pyi to make the Python version guards unconditional (since the contextlib2 API is the same on all supported versions)

• changes made to docs/contextlib2.rst to use contextlib2 version numbers in the version added/changed notes and to integrate the module documentation with the rest of the project documentation