Merge part of the trunk changes into the p3yk branch. This merges from 43030

(branch-creation time) up to 43067. 43068 and 43069 contain a little
swapping action between re.py and sre.py, and this mightily confuses svn
merge, so later changes are going in separately.

This merge should break no additional tests.

The last-merged revision is going in a 'last_merge' property on '.' (the
branch directory.) Arbitrarily chosen, really; if there's a BCP for this, I
couldn't find it, but we can easily change it afterwards ;)

Lib/StringIO.py

@@ -72,8 +72,7 @@ class StringIO:
         method is called repeatedly. This method returns the next input line,
         or raises StopIteration when EOF is hit.
         """
-        if self.closed:
-            raise StopIteration
+        _complain_ifclosed(self.closed)
         r = self.readline()
         if not r:
             raise StopIteration