Bite 12. Write a user validation function

Create a function that takes a username and checks for a valid user:

1. The username is in USERS,
2. the user is not expired, and
3. the user has the ADMIN role.

If those 3 conditions are met return SECRET.

If one of the conditions is not True raise an exception you define yourself: UserDoesNotExist, UserAccessExpired and UserNoPermission respectively. Check out the tests for more detail.

Have fun and keep calm and code in Python!