diff -r 1a5c72f9ff53 Lib/tempfile.py
--- a/Lib/tempfile.py	Fri Mar 20 11:32:17 2015 -0400
+++ b/Lib/tempfile.py	Sun Mar 22 12:21:21 2015 -0400
@@ -427,8 +427,10 @@
     # iter() doesn't use __getattr__ to find the __iter__ method
     def __iter__(self):
         # Don't return iter(self.file), but yield from it to avoid closing
-        # file as long as it's being used as iterator, see issue #23000.
-        # XXX Also don't use "yield from"!
+        # file as long as it's being used as iterator (see issue #23700).  We
+        # can't use 'yield from' here because iter(file) returns the file
+        # object itself, which has a close method, and thus the file would get
+        # closed when the generator is finalized, due to PEP380 semantics.
         for line in self.file:
             yield line