Allow transaction updateBlock to return Error instead of NSError

[darinf]

Unfortunately Error > NSError > Error is lossy on Windows.

enum MyErrorType: Error {
  case someError
}

Given code such as the above, if you convert an instance of MyErrorType to NSError, the result is no longer an instance of MyErrorType. This does not happen on Apple platforms.

This causes issues when trying to propagate an error generated from runTransaction's updateBlock to the caller of runTransaction.

A solution is to just use Error instead of NSError in the API.

[fiedukow]

nice find