'Return exported data which a spider yielding no ``items`` would return.'

@defer.inlineCallbacks
def exported_no_data(self, settings):

    class TestSpider(scrapy.Spider, ):
        name = 'testspider'
        start_urls = ['http://localhost:8998/']
        def parse(self, response):
            pass
    data = (yield self.run_and_export(TestSpider, settings))
    defer.returnValue(data)
