Make T8761 deterministic, I hope

Authored by simonmar on Jun 26 2016, 12:53 AM.

Description

Make T8761 deterministic, I hope

Summary:
T8761 seems to get different interleaving in its output on
Phabricator, so this switches it to use stderr consistently.

Test Plan: worksforme

Reviewers: goldfire, austin, bgamari, erikd

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2363