Asyncio issue 222 / PR 231 (Victor Stinner) -- fix @coroutine functions without __name__.
diff --git a/Lib/asyncio/futures.py b/Lib/asyncio/futures.py
index 2c741fd..74a99ba 100644
--- a/Lib/asyncio/futures.py
+++ b/Lib/asyncio/futures.py
@@ -162,7 +162,7 @@
             cb = ''
 
         def format_cb(callback):
-            return events._format_callback(callback, ())
+            return events._format_callback_source(callback, ())
 
         if size == 1:
             cb = format_cb(cb[0])