Summary: See D5874. PhutilDeferredLog's exception on `write()`/`__destruct()` is not especially important and can come at an awkward time. Instead of throwing, just emit an error message to the log.
Test Plan: Faked failed writes and saw an error message in the log instead of many terrible things everywhere.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T3144
Differential Revision: https://secure.phabricator.com/D5875
dc6c1bf435