More explanatory message

Author: NoahStapp

pymongo/asynchronous/mongo_client.py

@@ -1714,7 +1714,9 @@ async def _get_topology(self) -> Topology:
             if self._loop is None:
                 self._loop = asyncio.get_running_loop()
             elif self._loop != asyncio.get_running_loop():
-                raise RuntimeError("Cannot use AsyncMongoClient in different event loop")
+                raise RuntimeError(
+                    "Cannot use AsyncMongoClient in different event loop. AsyncMongoClient uses low-level asyncio APIs that bind it to the event loop it was created on."
+                )
         if not self._opened:
             if self._resolve_srv_info["is_srv"]:
                 await self._resolve_srv()

pymongo/synchronous/mongo_client.py

@@ -1708,7 +1708,9 @@ def _get_topology(self) -> Topology:
             if self._loop is None:
                 self._loop = asyncio.get_running_loop()
             elif self._loop != asyncio.get_running_loop():
-                raise RuntimeError("Cannot use MongoClient in different event loop")
+                raise RuntimeError(
+                    "Cannot use MongoClient in different event loop. MongoClient uses low-level asyncio APIs that bind it to the event loop it was created on."
+                )
         if not self._opened:
             if self._resolve_srv_info["is_srv"]:
                 self._resolve_srv()