Treat zero (0) timeout values as normal

aiohttp/helpers.py

@@ -477,7 +477,7 @@ def __enter__(self):
         if self._task is None:
             raise RuntimeError('Timeout context manager should be used '
                                'inside a task')
-        if self._timeout:
+        if self._timeout is not None:
             self._cancel_handler = self._loop.call_later(
                 self._timeout, self._cancel_task)
         return self
@@ -487,7 +487,7 @@ def __exit__(self, exc_type, exc_val, exc_tb):
             self._cancel_handler = None
             self._task = None
             raise asyncio.TimeoutError
-        if self._timeout:
+        if self._timeout is not None:
             self._cancel_handler.cancel()
             self._cancel_handler = None
         self._task = None

tests/test_timeout.py

@@ -50,15 +50,14 @@ def run():
     loop.run_until_complete(run())
 
 
-@pytest.mark.parametrize("delay", [None, 0])
 @pytest.mark.run_loop
-def test_timeout_disable(loop, delay):
+def test_timeout_disable(loop):
     @asyncio.coroutine
     def long_running_task():
         yield from asyncio.sleep(0.1, loop=loop)
         return 'done'
 
-    with Timeout(delay, loop=loop):
+    with Timeout(None, loop=loop):
         resp = yield from long_running_task()
     assert resp == 'done'