In the new version (scrapy 1.1) launched 2016-05-11 the crawl first downloads robots.txt before crawling. To change this behavior change in your settings.py
with ROBOTSTXT_OBEY
ROBOTSTXT_OBEY = False
Here are the release notes
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…