Python 3.4 introduced the inheritable attribute for FDs.  At the same
time, it changed the default so that all FDs are not inheritable by
default, that only inheritable FDs are inherited to subprocesses, and
only if close_fds is explicitly set to False.

Adhere to this by setting close_fds to False when working with
subprocesses that may want to inherit FDs, and by trying to
set_inheritable() on FDs that we do want to bequeath to them.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NEduardo Habkost <ehabkost@redhat.com>
Reviewed-by: NCleber Rosa <crosa@redhat.com>
Message-Id: <20181022135307.14398-7-mreitz@redhat.com>
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>