This affects pyexpat and _elementtree. PyExpat_CAPI now exposes a new
function - DefaultUnknownEncodingHandler.

Based on a patch by Serhiy Storchaka.

to interp->modules) and that deleting essential items from the dict
can cause Python to blow up.

Thanks to Terry Reedy for coming up with initial wording and Yogesh
Chaudhari for coming up with a patch using that wording in parallel to
my own patch.

Without this patch socket.getaddrinfo crashed when called
with some unusual argument combinations.

Patch by Guilherme Simões.

an internal XML encoding is UTF-8 or US-ASCII.

This has come up often enough now on the tracker that it deserves a FAQ entry.

Based on report and patch by Aaron Oakley.

Issue #17980: Fix possible abuse of ssl.match_hostname() for denial of service using certificates with many wildcards (CVE-2013-2099).

This caused an exception to be raised later than expected.

Use the cleaner looking @property style for __dict__.
Move _replace() to be just after make() to indicate that
it is a core method on named tuples.