Add RegistryBuilder for tests, and update crates-io error handling.#9126

Merged

bors merged 2 commits intorust-lang:masterfrom ehuss:registry-builder

Feb 3, 2021

+525-151

Commits on Feb 2, 2021

Add RegistryBuilder to help initializing test registries.
ehuss
committed

Commits on Feb 3, 2021

Add a ResponseError for registry API interaction.
ehuss
committed