Issue #16860: In tempfile, use O_CLOEXEC when available to set the
close-on-exec flag atomically.
#13094: add Programming FAQ entry about the behavior of closures.
#13094: merge with 3.2.
#13094: merge with 3.3.
Fix example by making the exception inherit from Exception.
Merge example fix with 3.2.
Merge example fix with 3.3.
Cleanup a few minor things.
#16862: remove outdated statements about Stackless.
#16862: merge with 3.2.
#16862: merge with 3.3.