From current `os` documentation:

> A file descriptor has an “inheritable” flag which indicates if the file descriptor can be inherited by child processes

from current `subprocess` documentation:

> If close_fds is true, all file descriptors except 0, 1 and 2 will be closed before the child process is executed

It would be helpful to explicitly specify that subprocess.Popen does not takes into account the inheritable flag ; thas is, that inheritable fds will still be closed with open_fds = False, and that non-inheritable fds will still be kept with open_fds = True.