use subprotocols from handshake

Author: aojea

kubernetes/base/stream/ws_client.py

@@ -73,6 +73,13 @@ def __init__(self, configuration, url, headers, capture_all, binary=False):
             self._all = _IgnoredIO()
         self.sock = create_websocket(configuration, url, headers)
         self.subprotocol = getattr(self.sock, 'subprotocol', None)
+        if not self.subprotocol and self.sock:
+            headers_dict = self.sock.getheaders()
+            if headers_dict:
+                for k, v in headers_dict.items():
+                    if k.lower() == 'sec-websocket-protocol':
+                        self.subprotocol = v
+                        break
         self._connected = True
         self._returncode = None