Allow pdm python install to use system certificates

[stfdxv]

Is your feature/enhancement proposal related to a problem? Please describe.

My machine is behind a corporate proxy, so SSL certificates from certifi won't work. When I do pdm python install 3.12 -v, I get an error.

Error

PS C:\Users\<username>> pdm python install 3.12 -v
STATUS: Downloading [email protected]
Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "c:\users\<username>\.local\bin\pdm.exe\__main__.py", line 7, in <module>
  File "C:\Users\<username>\pipx\venvs\pdm\Lib\site-packages\pdm\core.py", line 341, in main
    return core.main(args or sys.argv[1:])
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\<username>\pipx\venvs\pdm\Lib\site-packages\pdm\core.py", line 259, in main
    raise cast(Exception, err).with_traceback(traceback) from None
  File "C:\Users\<username>\pipx\venvs\pdm\Lib\site-packages\pdm\core.py", line 254, in main
    self.handle(project, options)
  File "C:\Users\<username>\pipx\venvs\pdm\Lib\site-packages\pdm\core.py", line 209, in handle
    command.handle(project, options)
  File "C:\Users\<username>\pipx\venvs\pdm\Lib\site-packages\pdm\cli\commands\python.py", line 99, in handle
    self.install_python(project, options.version)
  File "C:\Users\<username>\pipx\venvs\pdm\Lib\site-packages\pdm\cli\commands\python.py", line 124, in install_python
    original_filename = download(python_file, tf.name)
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\<username>\pipx\venvs\pdm\Lib\site-packages\pbs_installer\_install.py", line 99, in download
    with client.stream("GET", url, headers=_get_headers()) as resp:
  File "C:\Program Files\Python312\Lib\contextlib.py", line 137, in __enter__
    return next(self.gen)
           ^^^^^^^^^^^^^^
  File "C:\Users\<username>\pipx\venvs\pdm\Lib\site-packages\httpx\_client.py", line 870, in stream
    response = self.send(
               ^^^^^^^^^^
  File "C:\Users\<username>\pipx\venvs\pdm\Lib\site-packages\httpx\_client.py", line 914, in send
    response = self._send_handling_auth(
               ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\<username>\pipx\venvs\pdm\Lib\site-packages\httpx\_client.py", line 942, in _send_handling_auth
    response = self._send_handling_redirects(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\<username>\pipx\venvs\pdm\Lib\site-packages\httpx\_client.py", line 979, in _send_handling_redirects
    response = self._send_single_request(request)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\<username>\pipx\venvs\pdm\Lib\site-packages\httpx\_client.py", line 1015, in _send_single_request
    response = transport.handle_request(request)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\<username>\pipx\venvs\pdm\Lib\site-packages\httpx\_transports\default.py", line 232, in handle_request
    with map_httpcore_exceptions():
  File "C:\Program Files\Python312\Lib\contextlib.py", line 158, in __exit__
    self.gen.throw(value)
  File "C:\Users\<username>\pipx\venvs\pdm\Lib\site-packages\httpx\_transports\default.py", line 86, in map_httpcore_exceptions
    raise mapped_exc(message) from exc
httpx.ConnectError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1000)

Describe the solution you'd like

It would be great if pdm, while installing python, could use system certificates by default or expose a configuration switch to do it.