Per request delay implementation using request per_request_delay meta key #802

[GeorgeA92]

Changes in this PR provide possibility to set per request delays (as it explained in this #802 (comment))

 ....
    next =  response.css("li.next a ::attr(href)").extract_first()
    if next:
        yield scrapy.Request(url=response.urljoin(next),
                             callback=self.parse, meta={"per_request_delay": 3})

[codecov]

Codecov Report

Merging #3835 into master will increase coverage by 0.00%.
The diff coverage is 33.33%.

@@           Coverage Diff           @@
##           master    #3835   +/-   ##
=======================================
  Coverage   85.43%   85.44%           
=======================================
  Files         169      169           
  Lines        9649     9664   +15     
  Branches     1437     1441    +4     
=======================================
+ Hits         8244     8257   +13     
- Misses       1157     1158    +1     
- Partials      248      249    +1     

Impacted Files	Coverage Δ
scrapy/core/downloader/__init__.py	87.85% <33.33%> (-1.20%)	⬇️
scrapy/utils/reqser.py	94.11% <0.00%> (+1.80%)	⬆️