Deprecation warnings emitted by vendored six versions

[domdfcoding]

Description

The currently vendored versions of six (1.15 directly, https://github.com/pypa/pip/blob/main/src/pip/_vendor/six.py, 1.12 via urllib3 https://github.com/pypa/pip/blob/main/src/pip/_vendor/urllib3/packages/six.py) do not have the fixes for Python 3.10 added in benjaminp/six#343 and benjaminp/six#352.

See benjaminp/six#341 for context.

Vendoring six 1.16 will make the warnings go away. The latest version of urllib3 includes six 1.16.

Expected behavior

I did not expect any deprecation warnings related to this.

pip version

21.1.2

Python version

3.10.0b2

OS

Ubuntu 20.04

How to Reproduce

1. Create a virtualenv for Python 3.10
2. Run PYTHONWARNINGS=once pip --version
3. Observe several deprecation warnings in the form <frozen importlib._bootstrap>:914: ImportWarning: ....

To confirm the warnings were coming from the vendored versions of six I renamed the two instances of _SixMetaPathImporter to _VendoredSixMetaPathImporter (in _vendor) and _urllibSixMetaPathImporter (in _vendor/urllib3/packages).

Output

$ PYTHONWARNINGS=once pip --version
/tmp/310-venv/lib/python3.10/site-packages/pip/_vendor/packaging/tags.py:7: DeprecationWarning: The distutils package is deprecated and slated for removal in Python 3.12. Use setuptools or check PEP 632 for potential alternatives
  import distutils.util
<frozen importlib._bootstrap>:914: ImportWarning: _VendoredSixMetaPathImporter.find_spec() not found; falling back to find_module()
<frozen importlib._bootstrap>:671: ImportWarning: _VendoredSixMetaPathImporter.exec_module() not found; falling back to load_module()
<frozen importlib._bootstrap>:914: ImportWarning: _VendoredSixMetaPathImporter.find_spec() not found; falling back to find_module()
<frozen importlib._bootstrap>:914: ImportWarning: _urllibSixMetaPathImporter.find_spec() not found; falling back to find_module()
<frozen importlib._bootstrap>:671: ImportWarning: _urllibSixMetaPathImporter.exec_module() not found; falling back to load_module()
<frozen importlib._bootstrap>:914: ImportWarning: _VendoredSixMetaPathImporter.find_spec() not found; falling back to find_module()
<frozen importlib._bootstrap>:914: ImportWarning: _urllibSixMetaPathImporter.find_spec() not found; falling back to find_module()
<frozen importlib._bootstrap>:914: ImportWarning: _VendoredSixMetaPathImporter.find_spec() not found; falling back to find_module()
<frozen importlib._bootstrap>:914: ImportWarning: _urllibSixMetaPathImporter.find_spec() not found; falling back to find_module()
/usr/lib/python3.10/distutils/command/install.py:13: DeprecationWarning: The distutils.sysconfig module is deprecated, use sysconfig instead
  from distutils.sysconfig import get_config_vars
pip 21.1.2 from /tmp/310-venv/lib/python3.10/site-packages/pip (python 3.10)

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