Issue #21774: Fix incorrect variable in xml.dom.minidom
Isolate the subprocess test_close_fds_when_max_fd_is_lowered test so
that the rlimit calls happens in a child process rather than the
TestCase process to attempt to fix the gentoo buildbot's "Too many
open files" error.
fix a BytesWarning in my previous commit.
clarify when the list of subdirectories is read (closes #13779)