The Abseil version of `StatusOr` does not come with the status macros
or the `Consume*` family of functions.
This change modifies the existing code to use the common denominator
of the API that is available between Abseil's own implementation of
`StatusOr` and the one from Tensorflow that we are currently using.
Change-Id: I5c37f68636a1fd54d153f95d7303ab8644abb774
These tests are in preparation for factoring the Store away from libutil's Callback to absl::StatusOr.
They use the newly added MockBinaryCacheStore.
Updates: #25
Change-Id: I30c207589ec38254806ebc9a983f35668e353ae9
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1595
Tested-by: BuildkiteCI
Reviewed-by: glittershark <grfn@gws.fyi>