network: set _loop_thread again as it helps debugging

related: #6825

electrum/network.py

@@ -266,7 +266,11 @@ class Network(Logger, NetworkRetryManager[ServerAddr]):
 
         self.asyncio_loop = asyncio.get_event_loop()
         assert self.asyncio_loop.is_running(), "event loop not running"
-        self._loop_thread = None  # type: threading.Thread  # set by caller; only used for sanity checks
+        try:
+            self._loop_thread = self.asyncio_loop._mythread  # type: threading.Thread  # only used for sanity checks
+        except AttributeError as e:
+            self.logger.warning(f"asyncio loop does not have _mythread set: {e!r}")
+            self._loop_thread = None
 
         assert isinstance(config, SimpleConfig), f"config should be a SimpleConfig instead of {type(config)}"
         self.config = config

electrum/util.py

@@ -1187,6 +1187,7 @@ def create_and_start_event_loop() -> Tuple[asyncio.AbstractEventLoop,
                                          args=(stopping_fut,),
                                          name='EventLoop')
     loop_thread.start()
+    loop._mythread = loop_thread
     return loop, stopping_fut, loop_thread