code: def can_aquire_user_lock(repository_path, session_token):
      
      # NOTE ALWAYS use within lock access callback
  
      user_file_path = cpjoin(repository_path, 'user_file')
      if not os.path.isfile(user_file_path): return True
      with open(user_file_path, 'r') as fd2:
          content = fd2.read()
          if len(content) == 0: return True
          try: res = json.loads(content)
          except ValueError: return True
          if res['expires'] < int(time.time()): return True
          elif res['session_token'] == session_token: return True
      return False
docs: Allow a user to acquire the lock if no other user is currently using it, if the original
      user is returning, presumably after a network error, or if the lock has expired.