CrawlingLogsMiddleware truncating logs

[gutsytechster]

The middlewares when included in the SPIDER_MIDDLEWARES setting causes error from the callbacks to be truncated and shown like below

After I remove this middleware, the logs are shown with full traceback, showing which line cause the specific errors, which is the intentional behaviour.

[Gallaecio]

For the record, this is most likely because of the middleware casting the results iterable to a list instead of iterating it.