124: pip dependency resolver changes

pip is the package installer for Python. Often, when you run pip, especially the first time in a new virtual environment, you will see something like: WARNING: You are using pip version 20.1.1; however, version 20.2 is available. You should consider upgrading via the 'python -m pip install --upgrade pip' command. And you should. Because 20.2 has a new dependency resolver. Get in the habit, until October, of replacing pip install with pip install --use-feature=2020-resolver. This flag is new in the 20.2 release. This new pip dependency resolver is the result of a lot of work. Five of the people involved with this work are joining the show today: Bernard Tyers, Nicole Harris, Paul Moore, Pradyun Gedam, and Tzu-ping Chung. We talk about: pip dependency resolver changes user experience research and testing crafting good error messages efforts to improve the test suite testing pip with pytest some of the difficulties with testing pip working with a team on a large project working with a large code base bringing new developers into a large project Special Guests: Bernard Tyers, Nicole Harris, Paul Moore, Pradyun Gedam, and Tzu-ping Chung. Links: Changelog — pip 20.2 documentation — Including --use-feature=2020-resolver pypa/pip: The Python package installer — github repo testing pip - documentation pip - The Python Package Installer — pip 20.2 documentation Changes to the pip dependency resolver in 20.2 — Changes to the pip dependency resolver in 20.2