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.

Start by reproducing the installation with `python3 -m pip install python-language-server[all]` and compare it with `python -m pip install python-language-server[all]`, including which Python and kernel environments are used. Done means determining whether the issue belongs to this project and documenting or fixing the installation behavior and supported pip command.

Written by the indexing model from the issue text.