Currently the driver exposes the code name in an attribute of Mongo::Error::OperationFailure, but not in the exception message itself. It would be helpful for diagnostics if the code name was included in the exception message.

Since the message is being changed, I also suggest making it more clear that the error code (in parentheses) comes from the server. Especially for low numbered error codes (1-2 digits), to me, it is frequently not clear that the error code is server-generated.

Looking at the relevant code it seems there is quite a bit of logic to extract error messages from what I assume are ancient server responses of server versions that the driver no longer supports (pre-2.6). The parsing that predates 2.6, if identified, can be removed.

The following errors contain messages that are affected:

OperationFailure (add code name, change formatting)
BulkWriteError (code name not provided by server, change formatting to match OperationFailure)
Auth errors (code name already exposed, change formatting to match OperationFailure)