python-language-server[all] not working if installing with pip3

ice-python doesn't work when installing with the code `python3 -m pip install python-language-server[all]`. It does with `python -m pip install python-language-server[all]`. I have faced this problem in other packages, could someone explain me why does this happen?

As I have understood, pip is not going to be supported. So I'd rather prefer to install everything with pip3, instead of pip. Although, when I install a package with pip it's also available for python3 kernel.

I wouldn't like to have many duplicates, that's why I try to install all the packages with pip3. If you install with pip is the same than pip3? Problems like the one described above make me nuts to install packages with pip instead pip3.

首先使用 `python3 -m pip install python-language-server[all]` 重现安装过程，并将其与 `python -m pip install python-language-server[all]` 进行比较，包括确认所使用的 Python 和 kernel 环境。完成的标准是确定该问题是否属于此项目，并记录或修复安装行为以及受支持的 pip 命令。

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