No, I have to use close_fds=True, because I don't want to have the subprocess to inherit each and every file descriptor.
This is for two reasons:
i) Security - why should the subproces be able to work with all the parent processes' files?
ii) Sometimes, for whatever reason, the subprocess (Oracle Reports in this case) seems to hang. And because it inherited all of the parent's log file handles, the paraent can not close and remove its log files correctly. This is the reason why I stumbled about close_fds at all. BTW on MS Windows, a similar (but not equivalent) solution was to create the log files as non-inheritable.