asyncio: Handle error handler: enhance formatting of the callback
diff --git a/Lib/asyncio/events.py b/Lib/asyncio/events.py
index 4054482..58c6bd5 100644
--- a/Lib/asyncio/events.py
+++ b/Lib/asyncio/events.py
@@ -89,8 +89,8 @@
         try:
             self._callback(*self._args)
         except Exception as exc:
-            msg = 'Exception in callback {}{!r}'.format(self._callback,
-                                                        self._args)
+            cb = _format_callback(self._callback, self._args)
+            msg = 'Exception in callback {}'.format(cb)
             self._loop.call_exception_handler({
                 'message': msg,
                 'exception': exc,