asyncio.transports: Make _ProactorBasePipeTransport use _FlowControlMixin
diff --git a/Lib/asyncio/unix_events.py b/Lib/asyncio/unix_events.py
index 9a40c04..748452c 100644
--- a/Lib/asyncio/unix_events.py
+++ b/Lib/asyncio/unix_events.py
@@ -317,7 +317,7 @@
             self._loop = None
 
 
-class _UnixWritePipeTransport(selector_events._FlowControlMixin,
+class _UnixWritePipeTransport(transports._FlowControlMixin,
                               transports.WriteTransport):
 
     def __init__(self, loop, pipe, protocol, waiter=None, extra=None):