title: failed to create json file in scrapy
body: <p>I am trying to save scrapped data in json file. I have used scrapy to scrap the data from web.</p>
  
  <p>here is my spider code.</p>
  
  <pre><code>import scrapy
  import json
  
  class QuotesSpider(scrapy.Spider):
      name = 'quotes'
      allowed_domains = ['quotes.toscrape.com/page/1/']
      start_urls = ['http://quotes.toscrape.com/page/1//']
  
      def parse(self, response):
          with open('quotes.json', 'a') as f:
              for quote in response.css('div.quote'):
                  json.dump({
                       'text' : quote.css('span:text::text').extract_first(),
                       'author': quote.css('small.author::text').extract_first(),
                       'tags': quote.css('div.tags a.tag::text').extract(),
                       }, f)
  </code></pre>
  
  <p>When I execute this command <code>scrapy crawl quotes</code>, it finished successfully, but json file is not being created. </p>
  
  <p>Please tell me what I'm missing here.</p>