text: """Prompt user for yes/no answer to question.
  From:
  http://stackoverflow.com/questions/3041986/python-command-line-yes-no-input
  """
  
  import sys
  
  try:
      input = raw_input
  except NameError:
      # In Python 2 there is raw_input() that takes a string from stdin and
      # input() that takes a string from stdin and evaluates it. That last
      # function is not very useful and has been removed in Python 3, while
      # raw_input() has been renamed to input()
      pass
  
  def query_yes_no(question, default="yes"):
      """Ask a yes/no question via raw_input() and return their answer.
  
      Args:
          question (str): A string that is presented to the user.
          default (str): The presumed answer if the user just hits <Enter>. It
              must be "yes" (the default), "no" or None (meaning an answer is
              required of the user).
  
      Returns:
          (bool) True for "yes" or False for "no".
      """
      valid = {"yes": True, "y": True, "ye": True, "no": False, "n": False}
      if default is None:
          prompt = " [y/n] "
      elif default == "yes":
          prompt = " [Y/n] "
      elif default == "no":
          prompt = " [y/N] "
      else:
          raise ValueError("invalid default answer: '%s'" % default)
  
      while True:
          sys.stdout.write(question + prompt)
          choice = input().lower()
          if default is not None and choice == '':
              return valid[default]
          elif choice in valid:
              return valid[choice]
          else:
              sys.stdout.write("Please respond with 'yes' or 'no' "
                               "(or 'y' or 'n').\n")
  