Merged requested to merge topic/py3.6/basicauth-secfix into branch/py3.6
Port the patch from Python 3.6 (69cdeeb93e) to our stdlib:
The AbstractBasicAuthHandler class of the urllib.request module uses an inefficient regular expression which can be exploited by an attacker to cause a denial of service. Fix the regex to prevent the catastrophic backtracking. Vulnerability reported by Ben Caller and Matt Schwager.
AbstractBasicAuthHandler of urllib.request now parses all WWW-Authenticate HTTP headers and accepts multiple challenges per header: use the realm of the first Basic challenge.
--HG-- branch : py3.6