fix test_tornado_exception_can_be_caught RuntimeError: generator rais…

…ed StopIteration

vcr/cassette.py

@@ -126,20 +126,7 @@ def _handle_generator(self, fn):
         duration of the generator.
         """
         with self as cassette:
-            coroutine = fn(cassette)
-            # We don't need to catch StopIteration. The caller (Tornado's
-            # gen.coroutine, for example) will handle that.
-            to_yield = next(coroutine)
-            while True:
-                try:
-                    to_send = yield to_yield
-                except Exception:
-                    to_yield = coroutine.throw(*sys.exc_info())
-                else:
-                    try:
-                        to_yield = coroutine.send(to_send)
-                    except StopIteration:
-                        break
+            yield from fn(cassette)
 
     def _handle_function(self, fn):
         with self as cassette: