Create an event loop if it doesn't exist (#1857)

Python 3.14 has removed the implicit event loop creation. 

Announced in https://docs.python.org/dev/whatsnew/3.14.html#id7

Author: befeleme

fsspec/implementations/tests/test_http.py

@@ -443,7 +443,11 @@ def test_docstring():
 def test_async_other_thread(server):
     import threading
 
-    loop = asyncio.get_event_loop()
+    try:
+        loop = asyncio.get_event_loop()
+    except RuntimeError:  # Python 3.14+ codepath
+        loop = asyncio.new_event_loop()
+
     th = threading.Thread(target=loop.run_forever)
 
     th.daemon = True