pastebin - collaborative debugging

#!/usr/bin/env python
# youtube-dl-simple
# An adaption of the 'youtube-dl' script by Ricardo Garcia Gonzalez.
# Slight adaptions by Ricky Hewitt, Original by Ricardo Garcia Gonzalez.
# This adaption upon the original is merely intended to convert the URL, not download it.
# License: Public domain code

import urllib2, sys, re

std_headers = {
        'User-Agent': 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.1) Gecko/2008070208 Firefox/3.0.1',
        'Accept-Charset': 'ISO-8859-1,utf-8;q=0.7,*;q=0.7',
        'Accept': 'text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5',
        'Accept-Language': 'en-us,en;q=0.5',
}

def _real_extract(url):
    _VALID_URL = r'^((?:http://)?(?:\w+\.)?youtube\.com/(?:(?:v/)|(?:(?:watch(?:\.php)?)?\?(?:.+&)?v=)))?([0-9A-Za-z_-]+)(?(1).+)?$'

    # Extract video id from URL
    mobj = re.match(_VALID_URL, url)
    if mobj is None:
        print u'ERROR: invalid URL: %s' % (url)
        return [None]
    video_id = mobj.group(2)

    # Normalize URL, including format
    normalized_url = 'http://www.youtube.com/watch?v=%s' % video_id
    request = urllib2.Request(normalized_url, None, std_headers)
    try:
        video_webpage = urllib2.urlopen(request).read()
    except (urllib2.URLError, httplib.HTTPException, socket.error), err:
        print u'ERROR: unable to download video webpage: %s' % (str(err))
        return [None]

    # "t" param
    mobj = re.search(r', "t": "([^"]+)"', video_webpage)
    if mobj is None:
        print u'ERROR: unable to extract "t" parameter. Cannot download!'
        return [None]
    video_real_url = 'http://www.youtube.com/get_video?video_id=%s&t=%s' % (video_id, mobj.group(1))
    return video_real_url

if __name__=="__main__":
    import os

    if len(sys.argv) == 2:
        print _real_extract(sys.argv[1])
    else:
        print "Usage: " + sys.argv[0][sys.argv[0].rfind("\/")+1:len(sys.argv[0])] + " url"