Make Client strict
Make Client strict

Summary:
Could use a closer look. *Shouldn't* change semantics,
but there are some assumptions baked into the code
which I don't fully grasp.

Reviewed By: jknoxville

Differential Revision: D17282310

fbshipit-source-id: af8e6bcd188bd12180a7b2eeafee7ced4f44d1aa

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