Declare __await__ as coroutine.

Python 3.7 requires this.

Author: aaugustin

docs/changelog.rst

@@ -18,6 +18,8 @@ Changelog
 
 Also:
 
+* Added compatibility with Python 3.7.
+
 * :func:`~client.connect()` performs HTTP Basic Auth when the URI contains
   credentials.
 
@@ -126,6 +128,8 @@ Also:
 3.3
 ...
 
+* Ensured compatibility with Python 3.6.
+
 * Reduced noise in logs caused by connection resets.
 
 * Avoided crashing on concurrent writes on slow connections.

websockets/client.py

@@ -393,6 +393,7 @@ def __aenter__(self):
     def __aexit__(self, exc_type, exc_value, traceback):
         yield from self.ws_client.close()
 
+    @asyncio.coroutine
     def __await__(self):
         transport, protocol = yield from self._creating_connection
 

websockets/server.py

@@ -738,6 +738,7 @@ def __aexit__(self, exc_type, exc_value, traceback):
         self.ws_server.close()
         yield from self.ws_server.wait_closed()
 
+    @asyncio.coroutine
     def __await__(self):
         server = yield from self._creating_server
         self.ws_server.wrap(server)