(Merge 3.4) asyncio: sync with Tulip

* _WaitHandleFuture.cancel() now notify IocpProactor through the overlapped
  object that the wait was cancelled.
* Optimize IocpProactor.wait_for_handle() gets the result if the wait is
  signaled immediatly.
* Enhance representation of Future and Future subclasses

  - Add "created at filename:lineno" in the representation
  - Add Future._repr_info() method which can be more easily overriden than
    Future.__repr__(). It should now be more easy to enhance Future
    representation without having to modify each subclass. For example,
    _OverlappedFuture and _WaitHandleFuture get the new "created at" information.
  - Use reprlib to format Future result, and function arguments when formatting a
    callback, to limit the length of the representation.

* Fix repr(_WaitHandleFuture)
* _WaitHandleFuture and _OverlappedFuture: hide frames of internal calls in the
  source traceback.
* Cleanup ProactorIocp._poll(): set the timeout to 0 after the first call to
  GetQueuedCompletionStatus()
* test_locks: close the temporary event loop and check the condition lock
* Remove workaround in test_futures, no more needed

1 files changed, 10 insertions, 5 deletions

diff --git a/Lib/asyncio/events.py b/Lib/asyncio/events.py
index bddd7e3649..3c7a36d076 100644
--- a/Lib/asyncio/events.py
+++ b/Lib/asyncio/events.py
@@ -10,11 +10,12 @@ __all__ = ['AbstractEventLoopPolicy',
 
 import functools
 import inspect
-import subprocess
-import traceback
-import threading
+import reprlib
 import socket
+import subprocess
 import sys
+import threading
+import traceback
 
 
 _PY34 = sys.version_info >= (3, 4)
@@ -36,8 +37,12 @@ def _get_function_source(func):
 
 
 def _format_args(args):
-    # function formatting ('hello',) as ('hello')
-    args_repr = repr(args)
+    """Format function arguments.
+
+    Special case for a single parameter: ('hello',) is formatted as ('hello').
+    """
+    # use reprlib to limit the length of the output
+    args_repr = reprlib.repr(args)
     if len(args) == 1 and args_repr.endswith(',)'):
         args_repr = args_repr[:-2] + ')'
     return args_repr