Better error message for quantized dispatch (#28635)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/28635
Fixes #28518
Test Plan: Imported from OSS
Differential Revision: D18132566
Pulled By: z-a-f
fbshipit-source-id: 08acc3033b12a0b79b43a5346b7af100416ffa94
