AFAIU, this change broke the following usage of subprocess on Windows
(re-using a subprocess.STARTUPINFO instance to hide the command window):

    import os, subprocess

    STARTUPINFO = subprocess.STARTUPINFO()
    STARTUPINFO.dwFlags |= subprocess.STARTF_USESHOWWINDOW
    STARTUPINFO.wShowWindow = subprocess.SW_HIDE

    # raises OSError: [WinError 87]
    # in the second loop iteration starting with Python 3.7
    for i in range(2):
        print(i)
        with open(os.devnull, 'w') as stderr:
            subprocess.check_call(['attrib'], stderr=stderr,
                                  startupinfo=STARTUPINFO)

AFAICT, this works on Python 2.7, 3.4, 3.5, and 3.6