Summary:
Convert scm/mononoke to use failure, and update common/rust crates it depends on as well.
What it looks like is a lot of deleted code...
General strategy:
- common/rust/failure_ext adds some things that are in git failure that aren't yet in crates.io (`bail!` and `ensure!`, `Result<T, Error>`)
- everything returns `Result<T, failure::Error>`
- crates with real error get an error type, with a derived Fail implementation
- replicate error-chain by defining an `enum ErrorKind` where the fields match the declared errors in the error! macro
- crates with dummy error-chain (no local errors) lose it
- `.chain_err()` -> `.context()` or `.with_context()`
So far the only place I've needed to extract an error is in a unit test.
Having a single unified error type has simplified a lot of things, and removed a lot of error type parameters, error conversion, etc, etc.
Reviewed By: sid0
Differential Revision: D6446584
fbshipit-source-id: 744640ca2997d4a85513c4519017f2e2e78a73f5
