put asyncio fix into a function to make it more obvious where it starts and ends

webui.py

@@ -5,7 +5,6 @@ import importlib
 import signal
 import re
 import warnings
-import asyncio
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.middleware.gzip import GZipMiddleware
@@ -67,6 +66,19 @@ if cmd_opts.server_name:
 else:
     server_name = "0.0.0.0" if cmd_opts.listen else None
 
+
+def fix_asyncio_event_loop_policy():
+    """
+        The default `asyncio` event loop policy only automatically creates
+        event loops in the main threads. Other threads must create event
+        loops explicitly or `asyncio.get_event_loop` (and therefore
+        `.IOLoop.current`) will fail. Installing this policy allows event
+        loops to be created automatically on any thread, matching the
+        behavior of Tornado versions prior to 5.0 (or 5.0 on Python 2).
+    """
+
+    import asyncio
+
     if sys.platform == "win32" and hasattr(asyncio, "WindowsSelectorEventLoopPolicy"):
         # "Any thread" and "selector" should be orthogonal, but there's not a clean
         # interface for composing policies so pick the right base.
@@ -74,23 +86,11 @@ if sys.platform == "win32" and hasattr(asyncio, "WindowsSelectorEventLoopPolicy"
     else:
         _BasePolicy = asyncio.DefaultEventLoopPolicy
 
-
     class AnyThreadEventLoopPolicy(_BasePolicy):  # type: ignore
         """Event loop policy that allows loop creation on any thread.
-
-    The default `asyncio` event loop policy only automatically creates
-    event loops in the main threads. Other threads must create event
-    loops explicitly or `asyncio.get_event_loop` (and therefore
-    `.IOLoop.current`) will fail. Installing this policy allows event
-    loops to be created automatically on any thread, matching the
-    behavior of Tornado versions prior to 5.0 (or 5.0 on Python 2).
-
         Usage::
 
             asyncio.set_event_loop_policy(AnyThreadEventLoopPolicy())
-
-    .. versionadded:: 5.0
-
         """
 
         def get_event_loop(self) -> asyncio.AbstractEventLoop:
@@ -104,7 +104,6 @@ class AnyThreadEventLoopPolicy(_BasePolicy):  # type: ignore
                 self.set_event_loop(loop)
                 return loop
 
-
     asyncio.set_event_loop_policy(AnyThreadEventLoopPolicy())
 
 
@@ -140,6 +139,8 @@ Use --skip-version-check commandline argument to disable this check.
 
 
 def initialize():
+    fix_asyncio_event_loop_policy()
+
     check_versions()
 
     extensions.list_extensions()