[MERGE] Include formatted traceback in SmartMessageHandlerError details.

[Andrew Bennetts]

John Arbash Meinel wrote:
> Andrew Bennetts wrote:
> > This is just a simple patch to extend SmartMessageHandlerError a little.
> > I've found it very helpful when debugging my work on adding a
> > VersionedFiles.insert_record_stream RPC.
> > 
> > This would also help with diagnosing bugs like
> > <https://bugs.launchpad.net/bzr/+bug/304544>.
> > 
> > -Andrew.
> > 
> > 
> 
> This only effects debugging right? Otherwise I would think that seeing a
> formatted traceback as part of an already formatted traceback would be a
> bit weird.

Right.  The protocol decoder always catches this error, and calls
log_exception_quietly.  So it's in the log file (handy for test failures and
handy for bug reports), but nowhere else.

> Also, shouldn't there be a test in bzrlib/tests/test_errors.py that
> needs updating?

Good point.  Added.

-Andrew.