Graceful failure when S3 *(fake or real)* doesn't have key

* Directly related to #37. Stops net timeout when picking some other script that isn't present in fakeS3. Eventually when *aws-sdk* is updated this will be needed so it doesn't halt dev.

Possibly applicable routine to #486 for inline live migration
Merge pull request #487 from Martii/gracefulFailureTrap

Graceful failure when S3 *(fake or real)* doesn't have key

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