asyncio: update the doc
* dev: mention that the logging must be configured at DEBUG level
* streams: drain() has no more a strange return value, it's just
a standard coroutine
diff --git a/Doc/library/asyncio-stream.rst b/Doc/library/asyncio-stream.rst
index 11d13c8..a4a997e 100644
--- a/Doc/library/asyncio-stream.rst
+++ b/Doc/library/asyncio-stream.rst
@@ -172,17 +172,16 @@
Wait until the write buffer of the underlying transport is flushed.
- This method has an unusual return value. The intended use is to write::
+ The intended use is to write::
w.write(data)
yield from w.drain()
- When there's nothing to wait for, :meth:`drain()` returns ``()``, and the
- yield-from continues immediately. When the transport buffer is full (the
- protocol is paused), :meth:`drain` creates and returns a
- :class:`Future` and the yield-from will block until
- that Future is completed, which will happen when the buffer is
- (partially) drained and the protocol is resumed.
+ When the transport buffer is full (the protocol is paused), block until
+ the buffer is (partially) drained and the protocol is resumed. When there
+ is nothing to wait for, the yield-from continues immediately.
+
+ This method is a :ref:`coroutine <coroutine>`.
.. method:: get_extra_info(name, default=None)