Output to stderr in distributed tests. (#42139)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/42139
A bunch of tests were failing with buck since we would output to
stdout and buck would fail parsing stdout in some cases.
Moving these print statements to stderr fixes this issue.
ghstack-source-id: 108606579
Test Plan: Run the offending unit tests.
Reviewed By: mrshenli
Differential Revision: D22779135
fbshipit-source-id: 789af3b16a03b68a6cb12377ed852e5b5091bbad
