PB Delete, no error when key doesn't exist? [JIRA: RIAK-1739]

The proto file says RpbDelReq "will return a RpbDelResp on success or RpbErrorResp on failure."  I can get a RpbErrorResp if I send bogus params (rw to 999999, say).  But if I try to delete a key that does not exist, I get a RpbDelResp.  The HTTP interface works as I'd expect, giving me a 404 with "not found" body on deleting bogus keys.

What am I doing wrong?
