scrapy/scrapy — pull request #474 by redapple (2013-11-25 17:04:53+00:00)
Title: Do not send HTTP header if value for header key is None (fixes #473)

May not be the best place for it, and surely there is a nicer way to achieve the same thing.

If you set `headers={"Referer": None}`, you get `{'Referer': [None]}` at `HTTP11DownloadHandler` level.

Probably should be done also for HTTP/1.0