diff -r 20a5a56ce090 Lib/contextlib.py
--- a/Lib/contextlib.py	Wed Jan 07 13:14:47 2015 +1000
+++ b/Lib/contextlib.py	Thu Jan 08 21:37:01 2015 +1100
@@ -81,6 +81,11 @@
                 # was passed to throw().  This prevents a StopIteration
                 # raised inside the "with" statement from being suppressed
                 return exc is not value
+            except RuntimeError as exc:
+                # Likewise, suppress if that StopException got wrapped up.
+                if exc.__context__ is value:
+                    return False
+                raise
             except:
                 # only re-raise if it's *not* the exception that was
                 # passed to throw(), because __exit__() must not raise
diff -r 20a5a56ce090 Lib/difflib.py
--- a/Lib/difflib.py	Wed Jan 07 13:14:47 2015 +1000
+++ b/Lib/difflib.py	Thu Jan 08 21:37:01 2015 +1100
@@ -1516,6 +1516,7 @@
                 yield from_line,to_line,True
 
     def _line_pair_iterator():
+      try:
         """Yields from/to lines of text with a change indication.
 
         This function is an iterator.  It itself pulls lines from the line
@@ -1542,19 +1543,21 @@
             from_line, fromDiff = fromlines.pop(0)
             to_line, to_diff = tolines.pop(0)
             yield (from_line,to_line,fromDiff or to_diff)
+      except StopIteration:
+        pass # Stop when done
 
     # Handle case where user does not want context differencing, just yield
     # them up without doing anything else with them.
     line_pair_iterator = _line_pair_iterator()
     if context is None:
-        while True:
-            yield next(line_pair_iterator)
+        yield from line_pair_iterator
     # Handle case where user wants context differencing.  We must do some
     # storage of lines until we know for sure that they are to be yielded.
     else:
         context += 1
         lines_to_write = 0
-        while True:
+        try:
+          while True:
             # Store lines up until we find a difference, note use of a
             # circular queue because we only need to keep around what
             # we need for context.
@@ -1588,6 +1591,8 @@
                 else:
                     lines_to_write -= 1
                 yield from_line, to_line, found_diff
+        except StopIteration:
+            return # When the helper terminates, end.
 
 
 _file_template = """
diff -r 20a5a56ce090 Objects/genobject.c
--- a/Objects/genobject.c	Wed Jan 07 13:14:47 2015 +1000
+++ b/Objects/genobject.c	Thu Jan 08 21:37:01 2015 +1100
@@ -130,6 +130,26 @@
         }
         Py_CLEAR(result);
     }
+    else if (!result)
+    {
+        if (PyErr_ExceptionMatches(PyExc_StopIteration))
+        {
+            PyObject *exc, *val, *val2, *tb;
+            PyErr_Fetch(&exc, &val, &tb);
+            PyErr_NormalizeException(&exc, &val, &tb);
+            if (tb != NULL) {
+                PyException_SetTraceback(val, tb);
+            }
+            Py_DECREF(exc);
+            Py_XDECREF(tb);
+            PyErr_SetString(PyExc_RuntimeError,
+                "generator raised StopIteration");
+            PyErr_Fetch(&exc, &val2, &tb);
+            PyErr_NormalizeException(&exc, &val2, &tb);
+            PyException_SetCause(val2, val);
+            PyErr_Restore(exc, val2, tb);
+        }
+    }
 
     if (!result || f->f_stacktop == NULL) {
         /* generator can't be rerun, so release the frame */