code: def open_listing_page(trailing_part_of_url):
      
      base_url = 'http://www.bbc.co.uk/programmes/'
      print("Opening web page: " + base_url + trailing_part_of_url)
  
      try:
          html = requests.get(base_url + trailing_part_of_url).text
      except (IOError, NameError):
          print("Error opening web page.")
          print("Check network connection and/or programme id.")
          sys.exit(1)
  
      try:
          return lxml.html.fromstring(html)
      except lxml.etree.ParserError:
          print("Error trying to parse web page.")
          print("Maybe there's no programme listing?")
          sys.exit(1)
docs: Opens a BBC radio tracklisting page based on trailing part of url.
      Returns a lxml ElementTree derived from that page.
  
      trailing_part_of_url: a string, like the pid or e.g. pid/segments.inc