Inconsistent attribute access in asyncio.coroutine in debug mode

asyncio_debug_attr_access.py

"""
$ python3 --version
Python 3.4.3
$ python3 asyncio_debug_attr_access.py                                                                                                               
f result
$ PYTHONASYNCIODEBUG=X python3 asyncio_debug_attr_access.py 
Traceback (most recent call last):
  File "asyncio_debug_attr_access.py", line 21, in <module>
    print(loop.run_until_complete(coro_func()))
  File "/usr/lib/python3.4/asyncio/coroutines.py", line 154, in wrapper
    w.__name__ = func.__name__
  File "/usr/lib/python3.4/unittest/mock.py", line 570, in __getattr__
    raise AttributeError(name)
AttributeError: __name__
Exception ignored in: $
"""

import asyncio
import contextlib
from unittest.mock import Mock


def f():
    return "f result"

if __name__ == "__main__":
    loop = asyncio.get_event_loop()

    with contextlib.closing(loop):
        mocked_f = Mock(wraps=f)
        # Mocked function doesn't have special attributes like "__name__"
        assert not hasattr(mocked_f, "__name__")
        # In Python 3.4 with PYTHONASYNCIODEBUG asyncio.coroutine tries to get
        # mocked_f.__name__, which leads to error (looks like this behaviour is
        # fixed in Python 3.5).
        # Without PYTHONASYNCIODEBUG all works as expected.
        coro_func = asyncio.coroutine(mocked_f)
        print(loop.run_until_complete(coro_func()))
        mocked_f.assert_called_once_with()