Why I am Getting '_SIGCHLDWaker' object has no attribute 'doWrite' in Scrapy?

I am using Scrapy spiders inside Celery and I am getting this kind of errors randomly

Unhandled Error
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/twisted/python/log.py", line 103, in callWithLogger
    return callWithContext({"system": lp}, func, *args, **kw)
  File "/usr/lib/python2.7/site-packages/twisted/python/log.py", line 86, in callWithContext
    return context.call({ILogContext: newCtx}, func, *args, **kw)
  File "/usr/lib/python2.7/site-packages/twisted/python/context.py", line 122, in callWithContext
    return self.currentContext().callWithContext(ctx, func, *args, **kw)
  File "/usr/lib/python2.7/site-packages/twisted/python/context.py", line 85, in callWithContext
    return func(*args,**kw)
--- <exception caught here> ---
  File "/usr/lib/python2.7/site-packages/twisted/internet/posixbase.py", line 602, in _doReadOrWrite
    why = selectable.doWrite()
exceptions.AttributeError: '_SIGCHLDWaker' object has no attribute 'doWrite'

I am using:

celery==3.1.19
Django==1.9.4
Scrapy==1.3.0

This is how I run Scrapy inside Celery:

from billiard import Process
from scrapy.crawler import CrawlerProcess
from scrapy.utils.project import get_project_settings

class MyCrawlerScript(Process):
    def __init__(self, **kwargs):
        Process.__init__(self)
        settings = get_project_settings('my_scraper')
        self.crawler = CrawlerProcess(settings)
        self.spider_name = kwargs.get('spider_name')
        self.kwargs = kwargs

    def run(self):
        self.crawler.crawl(self.spider_name, qwargs=self.kwargs)
        self.crawler.start()

def my_crawl_manager(**kwargs):
    crawler = MyCrawlerScript(**kwargs)
    crawler.start()
    crawler.join()

Inside a celery task, I am calling:

my_crawl_manager(spider_name='my_spider', url='www.google.com/any-url-here')

Please any idea why this is happening?

P.S: I have asked another question Why I am Getting KeyError in Scrapy? I don't know if they are somehow similar

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