pip install scrapy-fake-useragent

DOWNLOADER_MIDDLEWARES = {
  'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware': None,
  'scrapy.downloadermiddlewares.retry.RetryMiddleware': None,
  'scrapy_fake_useragent.middleware.RandomUserAgentMiddleware': 400,
  'scrapy_fake_useragent.middleware.RetryUserAgentMiddleware': 401,
}