Cryptic `WinError` reported when subprocess execution fails with WSL path

Based on the investigation below, the most pragmatic change we can make here is to enhance the exception handling around the _winapi.CreateProcess call in subprocess such that the reported WinError that is raised when the command given is on a WSL path at least reports the offending command (the way os.startfile already does).

Original bug report

ensurepip fails on Windows venv creation with WSL UNC path

Bug description:

Running Python 3.12.3 from the Windows Store via Windows PowerShell, attempting to create a Windows virtual environment under a WSL UNC path fails:

PS Microsoft.PowerShell.Core\FileSystem::\\wsl$\fedoraremix\home\acoghlan\_build_win64> $windows_python="$((Get-Command python3).Path)"
PS Microsoft.PowerShell.Core\FileSystem::\\wsl$\fedoraremix\home\acoghlan\_build_win64> & "$windows_python" --version
Python 3.12.3
PS Microsoft.PowerShell.Core\FileSystem::\\wsl$\fedoraremix\home\acoghlan\_build_win64> & $windows_python -Im venv --copies test_venv
Error: [WinError 1] Incorrect function
PS Microsoft.PowerShell.Core\FileSystem::\\wsl$\fedoraremix\home\acoghlan\_build_win64> & $windows_python -Im venv --copies \\wsl$\fedoraremix\home\acoghlan\_build_win64\test_venv
Error: [WinError 1] Incorrect function

(I initially thought this might be related to #102584 , as it has some similarities to #102496, but there were enough differences that it seemed worthwhile to file a dedicated issue. The investigation below strongly supports the idea that this is a different problem, specifically with ensurepip trying to invoke a subprocess when sys.executable is pointing at an executable stored in a WSL folder)

CPython versions tested on:

3.12

Operating systems tested on:

Windows

Linked PRs

• gh-157713

Start at the subprocess entry point around the _winapi.CreateProcess call and review linked PR gh-157713 for the current implementation direction. Done means a failed command on a WSL path reports the offending command alongside the WinError, with the relevant subprocess behavior covered by tests.