Install a threading.excepthook on python 3.8 and later (#38741)

Exceptions in threads were being silently discarded and never
logged as the new in python 3.8 threading.excepthook was not
being set.

homeassistant/bootstrap.py

@@ -6,6 +6,7 @@ import logging
 import logging.handlers
 import os
 import sys
+import threading
 from time import monotonic
 from typing import TYPE_CHECKING, Any, Dict, Optional, Set
 
@@ -308,6 +309,12 @@ def async_enable_logging(
         "Uncaught exception", exc_info=args  # type: ignore
     )
 
+    if sys.version_info[:2] >= (3, 8):
+        threading.excepthook = lambda args: logging.getLogger(None).exception(
+            "Uncaught thread exception",
+            exc_info=(args.exc_type, args.exc_value, args.exc_traceback),
+        )
+
     # Log errors to a file if we have write access to file or config dir
     if log_file is None:
         err_log_path = hass.config.path(ERROR_LOG_FILENAME)