Rather than having to manually implement the exception-handling for the "DocException" message, we can instead re-use (and slightly extend) the existing `wrapReason` function since that one already does what we need.
Furthermore, we can also simplify handling of the "PasswordRequest" message a little bit and again re-use the `wrapReason` function.
Finally, the patch makes the following smaller changes:
- Avoid needlessly re-creating exceptions in the `wrapReason` function.
- Use a slightly shorter parameter name in the `wrapReason` function.
- Remove the unused entries in the `CallbackKind`/`StreamKind` enumerations.
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