The key with this question is to see it as a positive and as an opportunity to discuss your personal growth. The biggest mistake you can make with your answer is to say that you haven't had any failures. This will come across defensive and will damage your credibility.

Choose an answer that you can draw positives from and explain what you learnt from this failure. It's important to be accountable for your own mistakes so avoid blaming your failure on anyone else. Instead, explain why you failed and how you used this failure as a springboard for success.