refactor(mcp):used logger to log instead of print and updated unittes…

src/google/adk/tools/mcp_tool/mcp_session_manager.py

@@ -434,10 +434,9 @@ async def close(self):
           await exit_stack.aclose()
         except Exception as e:
           # Log the error but don't re-raise to avoid blocking shutdown
-          print(
-              'Warning: Error during MCP session cleanup for'
-              f' {session_key}: {e}',
-              file=self._errlog,
+          logger.warning(
+              f'Error during MCP session cleanup for {session_key}',
+              exc_info=True,
           )
         finally:
           del self._sessions[session_key]

tests/unittests/tools/mcp_tool/test_mcp_session_manager.py

@@ -388,7 +388,8 @@ async def test_close_success(self):
     assert len(manager._sessions) == 0
 
   @pytest.mark.asyncio
-  async def test_close_with_errors(self):
+  @patch("google.adk.tools.mcp_tool.mcp_session_manager.logger")
+  async def test_close_with_errors(self, mock_logger):
     """Test cleanup when some sessions fail to close."""
     manager = MCPSessionManager(self.mock_stdio_connection_params)
 
@@ -403,20 +404,18 @@ async def test_close_with_errors(self):
     manager._sessions["session1"] = (session1, exit_stack1)
     manager._sessions["session2"] = (session2, exit_stack2)
 
-    custom_errlog = StringIO()
-    manager._errlog = custom_errlog
-
     # Should not raise exception
     await manager.close()
 
     # Good session should still be closed
     exit_stack2.aclose.assert_called_once()
     assert len(manager._sessions) == 0
 
-    # Error should be logged
-    error_output = custom_errlog.getvalue()
-    assert "Warning: Error during MCP session cleanup" in error_output
-    assert "Close error 1" in error_output
+    # Error should be logged via logger.warning
+    mock_logger.warning.assert_called_once()
+    args, kwargs = mock_logger.warning.call_args
+    assert "Error during MCP session cleanup for session1" in args[0]
+    assert kwargs.get("exc_info")
 
   @pytest.mark.asyncio
   @patch("google.adk.tools.mcp_tool.mcp_session_manager.stdio_client")