def fetchLinks(self,url):
     dom = None
     try:
         response = urlopen(url)
         contenttype = response.info()['Content-Type']
         contenttype = contenttype.strip().lower()
         '''
         if the conten-type is not text/html the url is rejected as it could be images or something else
         that could not be parsed 
         '''
         if not contenttype.startswith('text/html'):
             self.log.debug('rejected = '+url+' Content-Type = '+contenttype)
             return
         dom = parse(response).getroot()
     except urllib.error.HTTPError as e1:
         self.log.warn(''.join(['HTTP error for ',url]))
         self.log.debug(e1,exc_info=sys.exc_info()[2]) 
         return
     except Exception as  e2:
         self.log.warn('cannot parse '+url)
         self.log.debug(e2,exc_info=sys.exc_info()[2]) 
         return
     if not dom is None:
         links = dom.cssselect('a')
         if not links is None:
             linksList = []
             for link in links:
                 if not link is None: 
                     href = link.get('href')
                     if href is None:
                         continue
                     suburl = URLValidator.formValidURL(url,href)
                     if not suburl is None:
                         linksList.append(suburl)
                     else:
                         self.log.debug('rejected href = '+href)
             if not linksList:
                 return None
             else:
                 return linksList
         f = open(lock,'w+')
         f.close()
     except:
         pass #even if lock file cannot be created proceed with the rest of the code
 log = None
 url = None
 maxlinks = None
 cmdlength = len(sys.argv)
 if cmdlength < 2 :
     print("Please enter url to crawl and the maximum number of links to be extracted which is an optional one")
     print("Eg 1: python Main.py http://python.org 50")
     print("Eg 2: python Main.py http://python.org")
     sys.exit()
 elif cmdlength == 2 or cmdlength == 3:
     url = str(sys.argv[1])
     if not URLValidator.isValidURL(url):
         print("Either your url is not valid or a format that cannot be crawled")
         sys.exit()
     if cmdlength == 3:
         try:
             maxlinks = int(sys.argv[2])
         except ValueError:
             print('Invalid maximum links')
             sys.exit()
         if maxlinks < 1:
             print("maximum links should be minimum 1")
             sys.exit()
 else:
     print("Invalid number of arguments")
     sys.exit()
 try: