(python plugin): fixes #1134

[gasuketsu]

Fixes #1134 .

According to my quick dig into python core plugin impl, python_path() that is used in PythonPlugin::install_default_package() and PythonPlugin::get_virtualenv() may point outdated python path when upgrading python@latest.
With this fix python_path() returns path based on ToolVersion::install_path() to avoid pointing outdated path during upgrade.

[jdx]

this won't work since it would just break the reason for adding this: #877

I think we can probably get by with using the short bin path for package installations and long form with virtualenv setup, however I'm not entirely sure if that will be enough.

[gasuketsu]

this won't work since it would just break the reason for adding this: #877

I think we can probably get by with using the short bin path for package installations and long form with virtualenv setup, however I'm not entirely sure if that will be enough.

Thanks for the feedback.
#1134 can be reproduced with virtualenv config like #877.
python in venv is always symlink points to specific version x.y.z (not x.y) and default packages are installed to ~/.local/share/rtx/installs/python/<version>/ even if we have virtualenv config.
So I think that both #877 and #1134 can be solved by keepin python_path() as is and using tv.install_path().join("bin/python") for installing default package.

I will prepare the change.