Django middleware for adding selected and ancestor classes to nav links

navurls.py

class NavURLs(object):
	def process_response(self, request, response):
		if response.has_header('Content-Type') and response['Content-Type'].startswith('text/html') and not response.has_header('Location') and response.status_code == 200:
			try:
				nav_search = re.compile('.*nav.*')
				content = BeautifulSoup(response.content)
				navs = content.body(lambda tag: tag.name == 'nav' or (tag.has_key('id') and nav_search.match(tag['id']) != None) or (tag.has_key('class') and nav_search.match(tag['class']) != None))
				for nav in navs:
					for link in nav("a"):
						if link['href'] == request.META['PATH_INFO']:
							link['class'] = 'selected' if not link.has_key('class') else link['class'] + ' selected'
						else:
							path = re.compile('^' + link['href'] + '(.+)')
							if path.match(request.META['PATH_INFO']):
								link['class'] = 'ancestor' if not link.has_key('class') else link['class'] + ' ancestor'
					response.content = content.renderContents()
			except:
				pass
		return response