Raise ValueError on no executable and empty args

[maximxlss]

Windows throws a cryptic OSError: [WinError 87] when trying to create a process with no executable and empty args, which confused me a lot. Doesn't work on Linux too and contradicts the purpose of Popen (as I understand it), so probably should be disallowed completely.

[bedevere-bot]

Most changes to Python require a NEWS entry.

Please add it using the blurb_it web app or the blurb command-line tool.

[cpython-cla-bot]

All commit authors signed the Contributor License Agreement.

[bedevere-bot]

Most changes to Python require a NEWS entry.

Please add it using the blurb_it web app or the blurb command-line tool.

[bedevere-bot]

Most changes to Python require a NEWS entry.

Please add it using the blurb_it web app or the blurb command-line tool.

[bedevere-bot]

Most changes to Python require a NEWS entry.

Please add it using the blurb_it web app or the blurb command-line tool.

[bedevere-bot]

Most changes to Python require a NEWS entry.

Please add it using the blurb_it web app or the blurb command-line tool.

[arhadthedev]

Thank you for a patch!

Could you post your exception message with a stack trace, please? On my Windows 10 Home 22H2, I get WinError 3 (no path found):

Running Release|x64 interpreter...
Python 3.12.0a7+ (heads/main-dirty:de18267685, Apr  5 2023, 22:28:44) [MSC v.1929 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from subprocess import Popen
>>> Popen(args=[], executable="")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "D:\Oleg\cpython\Lib\subprocess.py", line 1024, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "D:\Oleg\cpython\Lib\subprocess.py", line 1509, in _execute_child
    hp, ht, pid, tid = _winapi.CreateProcess(executable, args,
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
FileNotFoundError: [WinError 3] Системе не удается найти указанный путь

[maximxlss]

OSError: [WinError 87] is raised when you do subprocess.Popen([]), which is subprocess.Popen(args=[], executable=None). Happens because CreateProcess gets called with null executable and null args. FileNotFoundError: [WinError 3] does make sense in case of an empty path, I think.

In case of Linux, it causes an IndexError at trying to get the executable from the args.