title: Scrapy : Select tag with non-breaking space with xpath
body: <p>In my scrapy spider, i want to select only <code>&lt;p&gt;</code> with text content :   </p>
  
  <pre><code>item['Description'] = response.xpath('//*[@id="textepresentation"]//p[string(.)]').extract()
  </code></pre>
  
  <p>It works fine, but unfortunately, doing this, i also get empty <code>&lt;p&gt;</code> with non-breaking space </p>
  
  <pre><code>u'&lt;p&gt;\xa0&lt;/p&gt;',
  </code></pre>
  
  <p>How to avoid selecting <code>&lt;p&gt;</code> with non-breaking space with xpath ?</p>