The internal spawn function in ucrt, common_spawnv(), verifies its parameters as follows:

    _VALIDATE_RETURN(file_name       != nullptr, EINVAL, -1);
    _VALIDATE_RETURN(file_name[0]    != '\0',    EINVAL, -1);
    _VALIDATE_RETURN(arguments       != nullptr, EINVAL, -1);
    _VALIDATE_RETURN(arguments[0]    != nullptr, EINVAL, -1);
    _VALIDATE_RETURN(arguments[0][0] != '\0',    EINVAL, -1);

Currently os.spawnv() and os.spawnve() check for and raise ValueError for all of these cases except the second one, in which file_name is an empty string. Microsoft doesn't document this case [1]:

    These functions validate their parameters. If either cmdname or argv 
    is a null pointer, or if argv points to null pointer, or argv[0] is 
    an empty string, the invalid parameter handler is invoked, as 
    described in Parameter Validation.

In a release build, this case fails with EINVAL. In a debug build, the default error-reporting settings display a pop message about the invalid argument. The message box is easy enough to suppress. But for the sake of consistency with the other cases, os_spawnv_impl in Modules/posixmodule.c should raise a ValueError if `path` is an empty string. For example:

    #ifdef HAVE_WSPAWNV
        if (!path->wide[0]) {
            PyErr_SetString(PyExc_ValueError,
                "spawnv() arg 1 cannot be an empty string");
            return NULL;
        }
    #endif

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[1] https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/spawnv-wspawnv