stackoverflow 36391781 error

console.txt

$ scrapy crawl httpbin
2016-04-06 00:16:58 [scrapy] INFO: Scrapy 1.1.0rc3 started (bot: mwtest)
2016-04-06 00:16:58 [scrapy] INFO: Overridden settings: {'NEWSPIDER_MODULE': 'mwtest.spiders', 'SPIDER_MODULES': ['mwtest.spiders'], 'BOT_NAME': 'mwtest'}
2016-04-06 00:16:58 [scrapy] INFO: Enabled extensions:
['scrapy.extensions.logstats.LogStats',
 'scrapy.extensions.telnet.TelnetConsole',
 'scrapy.extensions.corestats.CoreStats']
2016-04-06 00:16:58 [py.warnings] WARNING: /home/paul/tmp/mwtest/mwtest/middlewares.py:1: ScrapyDeprecationWarning: Module `scrapy.log` has been deprecated, Scrapy now relies on the builtin Python library for logging. Read the updated logging entry in the documentation to learn more.
  from scrapy import log, signals

2016-04-06 00:16:58 [scrapy] INFO: Enabled downloader middlewares:
['scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',
 'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',
 'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',
 'scrapy.downloadermiddlewares.retry.RetryMiddleware',
 'mwtest.middlewares.TestMiddleware',
 'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',
 'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',
 'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',
 'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',
 'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',
 'scrapy.downloadermiddlewares.chunked.ChunkedTransferMiddleware',
 'scrapy.downloadermiddlewares.stats.DownloaderStats']
2016-04-06 00:16:58 [scrapy] INFO: Enabled spider middlewares:
['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',
 'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',
 'scrapy.spidermiddlewares.referer.RefererMiddleware',
 'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',
 'scrapy.spidermiddlewares.depth.DepthMiddleware']
2016-04-06 00:16:58 [scrapy] INFO: Enabled item pipelines:
[]
2016-04-06 00:16:58 [scrapy] INFO: Spider opened
2016-04-06 00:16:58 [scrapy] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2016-04-06 00:16:58 [httpbin] INFO: TestMiddleware.open_spider()
2016-04-06 00:16:58 [scrapy] DEBUG: Telnet console listening on 127.0.0.1:6023
2016-04-06 00:16:58 [scrapy] ERROR: Error caught on signal handler: <bound method ?.process of <mwtest.middlewares.TestMiddleware object at 0x7f83d4a73f50>>
Traceback (most recent call last):
  File "/home/paul/.virtualenvs/scrapy11rc3.py27/local/lib/python2.7/site-packages/scrapy/utils/signal.py", line 30, in send_catch_log
    *arguments, **named)
  File "/home/paul/.virtualenvs/scrapy11rc3.py27/local/lib/python2.7/site-packages/pydispatch/robustapply.py", line 55, in robustApply
    return receiver(*arguments, **named)
  File "/home/paul/tmp/mwtest/mwtest/middlewares.py", line 26, in process
    raise Exception
Exception
2016-04-06 00:16:58 [httpbin] INFO: TestMiddleware.process_request()
2016-04-06 00:16:58 [scrapy] ERROR: Error caught on signal handler: <bound method ?.process of <mwtest.middlewares.TestMiddleware object at 0x7f83d4a73f50>>
Traceback (most recent call last):
  File "/home/paul/.virtualenvs/scrapy11rc3.py27/local/lib/python2.7/site-packages/scrapy/utils/signal.py", line 30, in send_catch_log
    *arguments, **named)
  File "/home/paul/.virtualenvs/scrapy11rc3.py27/local/lib/python2.7/site-packages/pydispatch/robustapply.py", line 55, in robustApply
    return receiver(*arguments, **named)
  File "/home/paul/tmp/mwtest/mwtest/middlewares.py", line 26, in process
    raise Exception
Exception
2016-04-06 00:16:58 [httpbin] INFO: TestMiddleware.process_request()
2016-04-06 00:16:58 [scrapy] ERROR: Error caught on signal handler: <bound method ?.process of <mwtest.middlewares.TestMiddleware object at 0x7f83d4a73f50>>
Traceback (most recent call last):
  File "/home/paul/.virtualenvs/scrapy11rc3.py27/local/lib/python2.7/site-packages/scrapy/utils/signal.py", line 30, in send_catch_log
    *arguments, **named)
  File "/home/paul/.virtualenvs/scrapy11rc3.py27/local/lib/python2.7/site-packages/pydispatch/robustapply.py", line 55, in robustApply
    return receiver(*arguments, **named)
  File "/home/paul/tmp/mwtest/mwtest/middlewares.py", line 26, in process
    raise Exception
Exception
2016-04-06 00:16:58 [httpbin] INFO: TestMiddleware.process_request()
2016-04-06 00:16:58 [scrapy] ERROR: Error caught on signal handler: <bound method ?.process of <mwtest.middlewares.TestMiddleware object at 0x7f83d4a73f50>>
Traceback (most recent call last):
  File "/home/paul/.virtualenvs/scrapy11rc3.py27/local/lib/python2.7/site-packages/scrapy/utils/signal.py", line 30, in send_catch_log
    *arguments, **named)
  File "/home/paul/.virtualenvs/scrapy11rc3.py27/local/lib/python2.7/site-packages/pydispatch/robustapply.py", line 55, in robustApply
    return receiver(*arguments, **named)
  File "/home/paul/tmp/mwtest/mwtest/middlewares.py", line 26, in process
    raise Exception
Exception
2016-04-06 00:16:58 [httpbin] INFO: TestMiddleware.process_request()
2016-04-06 00:16:58 [scrapy] ERROR: Error caught on signal handler: <bound method ?.process of <mwtest.middlewares.TestMiddleware object at 0x7f83d4a73f50>>
Traceback (most recent call last):
  File "/home/paul/.virtualenvs/scrapy11rc3.py27/local/lib/python2.7/site-packages/scrapy/utils/signal.py", line 30, in send_catch_log
    *arguments, **named)
  File "/home/paul/.virtualenvs/scrapy11rc3.py27/local/lib/python2.7/site-packages/pydispatch/robustapply.py", line 55, in robustApply
    return receiver(*arguments, **named)
  File "/home/paul/tmp/mwtest/mwtest/middlewares.py", line 26, in process
    raise Exception
Exception
2016-04-06 00:16:58 [httpbin] INFO: TestMiddleware.process_request()
2016-04-06 00:16:58 [scrapy] DEBUG: Crawled (200) <GET http://www.httpbin.org/user-agent> (referer: None)
2016-04-06 00:16:58 [scrapy] DEBUG: Crawled (200) <GET http://www.httpbin.org/headers> (referer: None)
2016-04-06 00:16:58 [scrapy] DEBUG: Crawled (200) <GET http://www.httpbin.org/> (referer: None)
2016-04-06 00:16:58 [scrapy] INFO: Closing spider (finished)
2016-04-06 00:16:58 [scrapy] INFO: Dumping Scrapy stats:
{'downloader/exception_count': 2,
 'downloader/exception_type_count/scrapy.exceptions.IgnoreRequest': 2,
 'downloader/request_bytes': 665,
 'downloader/request_count': 3,
 'downloader/request_method_count/GET': 3,
 'downloader/response_bytes': 13006,
 'downloader/response_count': 3,
 'downloader/response_status_count/200': 3,
 'finish_reason': 'finished',
 'finish_time': datetime.datetime(2016, 4, 5, 22, 16, 58, 641313),
 'log_count/DEBUG': 4,
 'log_count/ERROR': 5,
 'log_count/INFO': 13,
 'log_count/WARNING': 1,
 'response_received_count': 3,
 'scheduler/dequeued': 5,
 'scheduler/dequeued/memory': 5,
 'scheduler/enqueued': 5,
 'scheduler/enqueued/memory': 5,
 'start_time': datetime.datetime(2016, 4, 5, 22, 16, 58, 221894)}
2016-04-06 00:16:58 [scrapy] INFO: Spider closed (finished)

httpbin.py

# -*- coding: utf-8 -*-
import scrapy


class HttpbinSpider(scrapy.Spider):
    name = "httpbin"
    allowed_domains = ["httpbin.org"]
    start_urls = (
        'http://www.httpbin.org/',
        'http://www.httpbin.org/ip',
        'http://www.httpbin.org/user-agent',
        'http://www.httpbin.org/get',
        'http://www.httpbin.org/headers',
    )

    def parse(self, response):
        pass

middlewares.py

from scrapy import log, signals
from scrapy.exceptions import IgnoreRequest

class TestMiddleware(object):

    def __init__(self, crawler):
        self.counter = 0

    @classmethod
    def from_crawler(cls, crawler):
        o = cls(crawler)
        crawler.signals.connect(o.open_spider, signals.spider_opened)
        
        # this raise an exception always and will trigger errors in the console
        crawler.signals.connect(o.process, signals.request_scheduled)
        return o

    def open_spider(self, spider):
        spider.logger.info('TestMiddleware.open_spider()')

    def process_request(self, request, spider):
        spider.logger.info('TestMiddleware.process_request()')
        self.counter += 1
        if (self.counter % 2) == 0:
            raise IgnoreRequest("ignoring request %d" % self.counter)

    def process(self, *args, **kwargs):
        raise Exception