code: def urljoin(*urls):
      
      return reduce(_urljoin, [u.strip('/')+'/' for u in urls if u.strip('/')], '').rstrip('/')
docs: The default urlparse.urljoin behavior look strange
      Standard urlparse.urljoin('http://a.com/foo', '/bar')
      Expect: http://a.com/foo/bar
      Actually: http://a.com/bar
  
      This function fix that.