pantsd not retaining / forwarding http_proxy env vars

[alextremblay]

Describe the bug
Just started using pants yesterday and ran across this error while trying to generate lockfiles:

$ pants generate-lockfiles 
16:20:51.53 [INFO] Initializing scheduler...
16:20:53.64 [INFO] Scheduler initialized.
...
16:29:37.97 [ERROR] 1 Exception encountered:

Engine traceback:
  in `generate-lockfiles` goal

IntrinsicError: Error downloading file: error sending request for url (https://github.com/astral-sh/python-build-standalone/releases/download/20250610/cpython-3.10.18%2B20250610-x86_64-unknown-linux-gnu-install_only_stripped.tar.gz)

Pants version
tested with pants 2.27 and 2.29

OS
Linux

Additional info
my pants.toml file:

[GLOBAL]
pants_version = "2.29.0"
backend_packages = [
    "pants.backend.python",
    "pants.backend.experimental.python.lint.ruff.check",
    "pants.backend.experimental.python.lint.ruff.format",
    "pants.backend.experimental.python.typecheck.pyright",
    "pants.backend.python.providers.experimental.python_build_standalone",
]

[python]
interpreter_constraints = ["CPython>=3.10,<3.11"]
enable_resolves = true

[subprocess-environment]
# pull in proxy settings from environment and pass them through to all subprocesses
env_vars = [
    "http_proxy",
    "https_proxy",
    "no_proxy",
    "HTTP_PROXY",
    "HTTPS_PROXY",
    "NO_PROXY",
]

I suspect #22725 is related. The creator of that issue is getting the same error and also mentions using a proxy. If so, then that person is misattributing their issue to a change in OS or pants version

[alextremblay]

After talking to @jsirois on slack, i came to realize that the subprocess-environment.env_vars config option does not actually behave the way the "Restricted Internet Access" page of the documentation led me to believe.

John had me try pants --no-pantsd generate-lockfiles, and it worked, which seems to imply that pantsd itself is not retaining / forwarding proxy-related env vars

[alextremblay]

@jsirois was kind enough to point me exactly where the problem lies: https://github.com/pantsbuild/pants/src/python/pants/pantsd/pants_daemon.py#L39C1-L54

we need to add the proxy-related variables to this list