Make msg() and msg_with_backtrace() private (#37094)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37094
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Test Plan: Imported from OSS
Differential Revision: D21202892
Pulled By: ezyang
fbshipit-source-id: d59e6bffabd90cc734056bdce2cd1fe63262fab8
