job queue: log the opcode error too

Currently we only log "Error in opcode ...", but we don't log the error itself.
This is not good for debugging.

Reviewed-by: ultrotter

lib/jqueue.py

@@ -424,8 +424,8 @@ class _JobQueueWorker(workerpool.BaseWorker):
                 op.status = constants.OP_STATUS_ERROR
                 op.result = str(err)
                 op.end_timestamp = TimeStampNow()
-                logging.info("Op %s/%s: Error in opcode %s", idx + 1, count,
-                             op_summary)
+                logging.info("Op %s/%s: Error in opcode %s: %s",
+                             idx + 1, count, op_summary, err)
               finally:
                 queue.UpdateJobUnlocked(job)
             finally: