.. original section: Library

Upgrade expat copy from 2.2.0 to 2.2.1 to get fixes of multiple security
vulnerabilities including: CVE-2017-9233 (External entity infinite loop
DoS), CVE-2016-9063 (Integer overflow, re-fix), CVE-2016-0718 (Fix
regression bugs from 2.2.0's fix to CVE-2016-0718) and CVE-2012-0876
(Counter hash flooding with SipHash). Note: the CVE-2016-5300 (Use os-
specific entropy sources like getrandom) doesn't impact Python, since Python
already gets entropy from the OS to set the expat secret using
``XML_SetHashSalt()``.
