move RaisesGroup import

Author: jakkdl

Diff for: tests/test_connection.py

@@ -50,6 +50,13 @@
 except ImportError:
     from trio.hazmat import current_task  # type: ignore # pylint: disable=ungrouped-imports
 
+
+# only available on trio>=0.25, we don't use it when testing lower versions
+try:
+    from trio.testing import RaisesGroup
+except ImportError:
+    pass
+
 from trio_websocket import (
     connect_websocket,
     connect_websocket_url,
@@ -460,7 +467,6 @@ async def handler(request):
         # 2. WebSocketServer.run
         # 3. trio.serve_listeners
         # 4. WebSocketServer._handle_connection
-        from trio.testing import RaisesGroup  # pylint: disable=import-outside-toplevel
         assert RaisesGroup(
             RaisesGroup(
                 RaisesGroup(