Exercise 9.3 is broken due to Coindesk API is no longer returning historical data by default

[mralebrije]

If we consume

https://api.coindesk.com/v1/bpi/historical/close.json

we are no longer getting the bpi node needed in the response to complete the exercise.

So, we need to update it to consume data for a previous date ex:

https://api.coindesk.com/v1/bpi/historical/close.json?start=2021-01-01&end=2021-03-01

BTW ❤️ thanks for your amazing courses.