update news and re doc

Doc/library/re.rst

@@ -478,6 +478,9 @@ functions are simplified versions of the full featured methods for compiled
 regular expressions.  Most non-trivial applications always use the compiled
 form.
 
+.. versionchanged:: 3.6
+   Flag constants are now instances of :class:`RegexFlag`, which is a subclass of
+   :class:`enum.IntFlag`.
 
 .. function:: compile(pattern, flags=0)
 

Misc/NEWS

@@ -726,6 +726,8 @@ Library
 - Issue #28025: Convert all ssl module constants to IntEnum and IntFlags.
   SSLContext properties now return flags and enums.
 
+- Issue #23591: Add Flag, IntFlag, and auto() to enum module.
+
 - Issue #433028: Added support of modifier spans in regular expressions.
 
 - Issue #24594: Validates persist parameter when opening MSI database