python - 什么是 --use-feature=2020-resolver？在 ubuntu 上安装 jupyter 的错误消息

Question

我正在尝试在 digital ocean 水滴上的 ubuntu 16.04.6 x64 上安装 jupyter。它给了我以下错误消息，我不明白这意味着什么。

ERROR: After October 2020 you may experience errors when installing or updating package
s. This is because pip will change the way that it resolves dependency conflicts. 

We recommend you use --use-feature=2020-resolver to test your packages with the new res
olver before it becomes the default.
 
jsonschema 3.2.0 requires six>=1.11.0, but you'll have six 1.10.0 which is incompatible

任何帮助将不胜感激!

Answer 1

根据this announcement ，pip 将在 2020 年 10 月引入一个新的依赖解析器，它会更加强大，但可能会破坏一些现有的设置。因此，他们建议用户尝试使用此选项至少运行一次他们的 pip 安装脚本(在开发模式下):--use-feature=2020-resolver在新的解析器成为 2020 年 10 月 pip 版本 20.3 的默认值之前预测任何潜在问题。

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 directlyrequested 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).