pdm install does not enforce requires-python

[gusalecar]

• I have searched the issue tracker and believe that this is not a duplicate.

Make sure you run commands with -v flag before pasting the output.

Steps to reproduce

With this pyproject.toml

[project]
dependencies = [
    "flatdict>=4.0.1",
]
requires-python = "~=3.9.0"

pdm install -v

python.use_venv is on, creating a virtualenv for this project...
Run command: ['/home/gus/.local/pipx/venvs/pdm/bin/python', '-m', 'virtualenv', 
'--no-pip', '--no-setuptools', '--no-wheel', '/home/gus/Escritorio/test/.venv', 
'-p', '/usr/bin/python3']
created virtual environment CPython3.10.4.final.0-64 in 62ms
  creator CPython3Posix(dest=/home/gus/Escritorio/test/.venv, clear=False, no_vcs_ignore=False, global=False)
  activators BashActivator,CShellActivator,FishActivator,NushellActivator,PowerShellActivator,PythonActivator
Virtualenv is created successfully at /home/gus/Escritorio/test/.venv
Synchronizing working set with lock file: 1 to add, 0 to update, 0 to remove

unearth: Downloading <Link https://files.pythonhosted.org/packages/3e/0d/424de6e5612f1399ff69bf86500d6a62ff0a4843979701ae97f120c7f1fe/flatdict-4.0.1.tar.gz (from None)> to /tmp/pdm-download-860bv6l7/flatdict-4.0.1.tar.gz
pdm.termui: Using cached wheel: /home/gus/.cache/pdm/wheels/ef/c0/10/643b3daf88e1a913d0554997ed1e5f5b7b69a57a05fb34d0a9/flatdict-4.0.1-py3-none-any.whl
  ✔ Install flatdict 4.0.1 successful

🎉 All complete!

Actual behavior

It uses the system installed Python, in this case 3.10

Expected behavior

It should block installation

Environment Information

Don't know why but it creates __pypackages__ folder and detects correct Python version

# Paste the output of `pdm info && pdm info --env` below:
PDM version:
  2.0.1
Python Interpreter:
  /home/gus/.pyenv/versions/3.9.13/bin/python3.9 (3.9)
Project Root:
  /home/gus/Escritorio/test
Project Packages:
  /home/gus/Escritorio/test/__pypackages__/3.9
{
  "implementation_name": "cpython",
  "implementation_version": "3.9.13",
  "os_name": "posix",
  "platform_machine": "x86_64",
  "platform_release": "5.15.0-41-generic",
  "platform_system": "Linux",
  "platform_version": "#44-Ubuntu SMP Wed Jun 22 14:20:53 UTC 2022",
  "python_full_version": "3.9.13",
  "platform_python_implementation": "CPython",
  "python_version": "3.9",
  "sys_platform": "linux"
}