Basic error handling
Basic error handling

Summary:
Adds some very basic error handling. It's not great
because once you hit an error, you're basically stuck
and there's no retry yet, but it's still strictly
an improvement over being stuck with the looping
spinner, so I think it's worth shipping it in this state.

Reviewed By: jknoxville

Differential Revision: D17763467

fbshipit-source-id: b5b7996554dd1dce682fba87f96e3806432a475a

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