only raise if the event loop is running

hail/python/hailtop/__init__.py

@@ -46,25 +46,27 @@ def main_thread_event_loop():
     import threading  # pylint: disable=import-outside-toplevel
     import nest_asyncio  # pylint: disable=import-outside-toplevel
 
-    if _hail_created_the_main_thread_event_loop:
-        raise ValueError(
-            'As a matter of Hail team policy, you are not allowed to nest asynchronous Hail code '
-            'inside synchronous Hail code.'
-        )
-
     try:
         asyncio.get_running_loop()
         nest_asyncio.apply()
         return asyncio.get_running_loop()
     except RuntimeError as err:
         assert err.args[0] == "no running event loop"
+
         if threading.current_thread() is not threading.main_thread():
             raise ValueError(
                 'Hail will not create an event loop outside of the Main Thread. Create one '
                 'yourself with asyncio.set_event_loop before initializing Hail if you want to run '
                 'Hail outside the Main Thread. Note that Hail is not thread-safe. Current thread: '
                 f'{threading.current_thread()}'
             ) from err
+
+        if _hail_created_the_main_thread_event_loop:
+            raise ValueError(
+                'As a matter of Hail team policy, you are not allowed to nest asynchronous Hail code '
+                'inside synchronous Hail code.'
+            ) from err
+
         loop = asyncio.new_event_loop()
         asyncio.set_event_loop(loop)
         _hail_created_the_main_thread_event_loop = True