After discussing some more with Georg, do no migrate versionchanged:: 2.5 to
this branch. While I am here, also get rid of other versionchanged:: 2.x
constructs, as discussed.
diff --git a/Doc/library/re.rst b/Doc/library/re.rst
index fade6ec..1259b11 100644
--- a/Doc/library/re.rst
+++ b/Doc/library/re.rst
@@ -605,7 +605,7 @@
       >>> re.split("(?m)^$", "foo\n\nbar\n")
       ['foo\n\nbar\n']
 
-   .. versionchanged:: 2.7,3.1
+   .. versionchanged:: 3.1
       Added the optional flags argument.
 
 
@@ -675,7 +675,7 @@
    character ``'0'``.  The backreference ``\g<0>`` substitutes in the entire
    substring matched by the RE.
 
-   .. versionchanged:: 2.7,3.1
+   .. versionchanged:: 3.1
       Added the optional flags argument.
 
 
@@ -684,7 +684,7 @@
    Perform the same operation as :func:`sub`, but return a tuple ``(new_string,
    number_of_subs_made)``.
 
-   .. versionchanged:: 2.7,3.1
+   .. versionchanged:: 3.1
       Added the optional flags argument.