Support websockets 8.x as well as 7.x (#1687)

Sanic currently requires websockets 7.x, but it's straightforward to
also support the more recent 8.x.

sanic/websocket.py

@@ -119,6 +119,9 @@ class WebSocketProtocol(HttpProtocol):
             read_limit=self.websocket_read_limit,
             write_limit=self.websocket_write_limit,
         )
+        # Following two lines are required for websockets 8.x
+        self.websocket.is_client = False
+        self.websocket.side = "server"
         self.websocket.subprotocol = subprotocol
         self.websocket.connection_made(request.transport)
         self.websocket.connection_open()

setup.py

@@ -80,7 +80,7 @@ requirements = [
     uvloop,
     ujson,
     "aiofiles>=0.3.0",
-    "websockets>=7.0,<8.0",
+    "websockets>=7.0,<9.0",
     "multidict>=4.0,<5.0",
     "requests-async==0.5.0",
 ]