Issue #13916: Disallowed the surrogatepass error handler for non UTF-*
encodings.
Issue #21486: Optimize parsing of netmasks in ipaddress.IPv4Network and ipaddress.IPv6Network.
Issue #21487: Optimize ipaddress.summarize_address_range() and ipaddress.{IPv4Network,IPv6Network}.subnets().
Issue #20826: Optimize ipaddress.collapse_addresses().
Issue #21364: remove recommendation of broken pattern.
Issue #21364: remove recommendation of broken pattern.
Better organization of the what's new
Mention ipaddress improvements.
Issue #18104: revise docstrings, remove obsolete comments.
Merge with 3.4