【Poetry】EnvCommandErrorの対処法と、Pythonを更新（3.9にアップデート）する流れ

[EnvCommandError]

[tool.poetry.dependencies]
python = "3.9"

[EnvCommandError]
Command python3.9 -c "import sys; print('.'.join([str(s) for s in sys.version_info[:3]]))" errored with the following return code 127, and output:

poetry env info

Virtualenv
Python:         2.7.16
Implementation: CPython
Path:           NA

System
Platform: darwin
OS:       posix
Python:   /System/Library/Frameworks/Python.framework/Versions/2.7

PATH="/Library/Frameworks/Python.framework/Versions/3.9/bin:${PATH}"

PATH="${HOME}/Library/Python/3.9/bin:${PATH}"

export PATH

poetry env info

Platform: darwin
OS:       posix
Python:   /System/Library/Frameworks/Python.framework/Versions/2.7

poetry env use 3.9

[NoCompatiblePythonVersionFound]
The specified Python version (3.9.2) is not supported by the project (3.9).
Please choose a compatible version or loosen the python constraint specified in the pyproject.toml file.

[tool.poetry.dependencies]
python = "3.9.2"

poetry env use 3.9

Creating virtualenv test in /Users/xxxxxxxxxxxx/Desktop/test/.venv
Using virtualenv: /Users/xxxxxxxxxxxx/Desktop/test/.venv

poetry env info

Virtualenv
Python:         3.9.2
Implementation: CPython
Path:           /Users/xxxxxxxxxxxx/Desktop/test/.venv
Valid:          True

System
Platform: darwin
OS:       posix
Python:   /Library/Frameworks/Python.framework/Versions/3.9