asyncio doc: remove reference to _DEBUG (now replaced with PYTHONASYNCIODEBUG
env var), document the default debug mode
diff --git a/Doc/library/asyncio-dev.rst b/Doc/library/asyncio-dev.rst
index c5f0d1a..9d6f054 100644
--- a/Doc/library/asyncio-dev.rst
+++ b/Doc/library/asyncio-dev.rst
@@ -98,7 +98,6 @@
 Example with the bug::
 
     import asyncio
-    asyncio.tasks._DEBUG = True
 
     @asyncio.coroutine
     def test():
diff --git a/Doc/library/asyncio-eventloop.rst b/Doc/library/asyncio-eventloop.rst
index 04b182b..92c4978 100644
--- a/Doc/library/asyncio-eventloop.rst
+++ b/Doc/library/asyncio-eventloop.rst
@@ -558,7 +558,7 @@
 
 .. method:: BaseEventLoop.get_debug()
 
-   Get the debug mode (:class:`bool`) of the event loop.
+   Get the debug mode (:class:`bool`) of the event loop, ``False`` by default.
 
 .. method:: BaseEventLoop.set_debug(enabled: bool)