Generated a fresh captcha

        This method randomly generates a simple captcha question. It then
        generates a timestamp for the current time, and signs the answer
        cryptographically to protect against tampering and replay attacks.

def generate_captcha(self):
        """Generated a fresh captcha

        This method randomly generates a simple captcha question. It then
        generates a timestamp for the current time, and signs the answer
        cryptographically to protect against tampering and replay attacks.
        """
        # Generate a fresh question
        self._question, answer = self._generate_question()

        # Get the current time, then sign the answer cryptographically
        timestamp = time.time()
        hashed = self.hash_answer(answer, timestamp)

        # Now stash all our values
        self._values = ['', timestamp, hashed]