what is --use-feature=2020-resolver? error message with jupyter installation on ubuntu

According to this announcement, pip will introduce a new dependency resolver in October 2020, which will be more robust but might break some existing setups. Therefore they are suggesting users to try running their pip install scripts at least once (in dev mode) with this option: --use-feature=2020-resolver to anticipate any potential issue before the new resolver becomes the default in October 2020 with pip version 20.3.

On behalf of the PyPA, I am pleased to announce that we have just released pip 20.2, a new version of pip. You can install it by running python -m pip install --upgrade pip.

The highlights for this release are:

• The beta of the next-generation dependency resolver is available
• Faster installations from wheel files
• Improved handling of wheels containing non-ASCII file contents
• Faster pip list using parallelized network operations
• Installed packages now contain metadata about whether they were directly requested by the user (PEP 376’s REQUESTED file)

The new dependency resolver is off by default because it is not yet ready for everyday use.

The new dependency resolver is significantly stricter and more consistent when it receives incompatible instructions, and reduces support for certain kinds of constraints files, so some workarounds and workflows may break. Please test it with the --use-feature=2020-resolver flag. Please see our guide on how to test and migrate, and how to report issues . We are preparing to change the default dependency resolution behavior and make the new resolver the default in pip 20.3 (in October 2020).

First check if your pip is updated:

python -m pip install --upgrade pip

and then use:

pip install example --use-feature=2020-resolver

It worked for me.