Duplicated feed logs with BlockingFeedStorage

test.py

from time import sleep

import scrapy
from scrapy.extensions.feedexport import BlockingFeedStorage


class GsFeedStorage(BlockingFeedStorage):

    def __init__(self, uri):
        self.uri = uri

    def _store_in_thread(self, file):
        sleep(2)


class QuotesSpider(scrapy.Spider):
    name = 'quotes'
    start_urls = ['http://quotes.toscrape.com/']

    custom_settings = {
        'FEEDS': {
            'gs://bucket/output.json': {'format': 'json'},
            'gs://bucket/output.csv': {'format': 'csv'}
        },
        'FEED_STORAGES': {'gs': 'test.GsFeedStorage'}
    }

    def parse(self, response):
        for quote in response.css('div.quote'):
            yield {
                'text': quote.css('.text::text').get(),
                'author': quote.css('.author::text').get(),
                'tags': quote.css('a.tag::text').getall()
            }