[websocket] Make syntax error in `websockets` module non-fatal

Closes #2633

yt_dlp/downloader/websocket.py

@@ -5,9 +5,12 @@ import threading
 
 try:
     import websockets
-    has_websockets = True
+except (ImportError, SyntaxError):
-except ImportError:
+    # websockets 3.10 on python 3.6 causes SyntaxError
+    # See https://github.com/yt-dlp/yt-dlp/issues/2633
     has_websockets = False
+else:
+    has_websockets = True
 
 from .common import FileDownloader
 from .external import FFmpegFD