provide better error message when disabling s3 exporter
provide better error message when disabling s3 exporter

starrify/scrapy,pawelmhm/scrapy,eLRuLL/scrapy,Ryezhang/scrapy,kmike/scrapy,Ryezhang/scrapy,elacuesta/scrapy,dangra/scrapy,starrify/scrapy,finfish/scrapy,kmike/scrapy,eLRuLL/scrapy,scrapy/scrapy,wujuguang/scrapy,pawelmhm/scrapy,ArturGaspar/scrapy,pablohoffman/scrapy,wujuguang/scrapy,pawelmhm/scrapy,elacuesta/scrapy,eLRuLL/scrapy,scrapy/scrapy,dangra/scrapy,ArturGaspar/scrapy,kmike/scrapy,Ryezhang/scrapy,pablohoffman/scrapy,starrify/scrapy,finfish/scrapy,ArturGaspar/scrapy,dangra/scrapy,pablohoffman/scrapy,elacuesta/scrapy,finfish/scrapy,scrapy/scrapy,wujuguang/scrapy