title: scrapy item loader to get a absolute url from extracted url
body: <p>I am using/learning <code>scrapy</code>, python framework to scrape few of my interested web pages. In that go I extract the links in a page. But those links are relative in most of the case. I used <code>urljoin_rfc</code> which is present in <code>scrapy.utils.url</code> to get the absolute path. It worked fine.</p>
  
  <p>In a process of learning I came across a feature called <code>Item Loader</code>. Now I want to do the same using Item loader. My <code>urljoin_rfc()</code> is in a user defined function function <code>_urljoin(url,response)</code>. I want my loader to refer the function <code>_urljoin</code> now. So in my loader class I do <code>link_in = _urljoin()</code>. So I canged my _urljoin declaration to <code>_urljoin(url, response = loader_context.response)</code>. 
  But I get a error saying <code>NameError: name 'loader_context' is not defined</code>   </p>
  
  <p>I need help here. I do this because, not just while loading I call _urljoin(), other part of my code too call the function _urljoin. If i am terribly doing bad please bring it to my notice.  </p>