PYTHON-1290 Convert asyncio reactor away from @asyncio.coroutine

cassandra/io/asyncioreactor.py

@@ -46,9 +46,8 @@ def __init__(self, timeout, callback, loop):
         self._handle = asyncio.run_coroutine_threadsafe(delayed, loop=loop)
 
     @staticmethod
-    @asyncio.coroutine
-    def _call_delayed_coro(timeout, callback, loop):
-        yield from asyncio.sleep(timeout, loop=loop)
+    async def _call_delayed_coro(timeout, callback, loop):
+        await asyncio.sleep(timeout, loop=loop)
         return callback()
 
     def __lt__(self, other):
@@ -136,8 +135,7 @@ def close(self):
             self._close(), loop=self._loop
         )
 
-    @asyncio.coroutine
-    def _close(self):
+    async def _close(self):
         log.debug("Closing connection (%s) to %s" % (id(self), self.endpoint))
         if self._write_watcher:
             self._write_watcher.cancel()
@@ -174,40 +172,39 @@ def push(self, data):
             # avoid races/hangs by just scheduling this, not using threadsafe
             self._loop.create_task(self._push_msg(chunks))
 
-    @asyncio.coroutine
-    def _push_msg(self, chunks):
+    async def _push_msg(self, chunks):
         # This lock ensures all chunks of a message are sequential in the Queue
-        with (yield from self._write_queue_lock):
+        with await self._write_queue_lock:
             for chunk in chunks:
                 self._write_queue.put_nowait(chunk)
 
 
-    @asyncio.coroutine
-    def handle_write(self):
+    async def handle_write(self):
         while True:
             try:
-                next_msg = yield from self._write_queue.get()
+                next_msg = await self._write_queue.get()
                 if next_msg:
-                    yield from self._loop.sock_sendall(self._socket, next_msg)
+                    await self._loop.sock_sendall(self._socket, next_msg)
             except socket.error as err:
                 log.debug("Exception in send for %s: %s", self, err)
                 self.defunct(err)
                 return
             except asyncio.CancelledError:
                 return
 
-    @asyncio.coroutine
-    def handle_read(self):
+    async def handle_read(self):
         while True:
             try:
-                buf = yield from self._loop.sock_recv(self._socket, self.in_buffer_size)
+                buf = await self._loop.sock_recv(self._socket, self.in_buffer_size)
                 self._iobuf.write(buf)
             # sock_recv expects EWOULDBLOCK if socket provides no data, but
             # nonblocking ssl sockets raise these instead, so we handle them
             # ourselves by yielding to the event loop, where the socket will
             # get the reading/writing it "wants" before retrying
             except (ssl.SSLWantWriteError, ssl.SSLWantReadError):
-                yield
+                # Apparently the preferred way to yield to the event loop from within
+                # a native coroutine based on https://github.com/python/asyncio/issues/284
+                await asyncio.sleep(0)
                 continue
             except socket.error as err:
                 log.debug("Exception during socket recv for %s: %s",