There are no old-style classes in Python 3. If a class doesn't inherit from anything than it is implicitly inherits from object.

Exactly what I was thinking

@jacobb: Yeah, it lets your objects use super(): http://rhettinger.wordpress.com/2011/05/26/super-considered-super/

Ugh, not best practices to use old-style classes.

You should probably inherit from object, according to the Google Style Guide at least.

The test case should be revised to test for edge case solutions as I saw that somebody's solution has passed but it didn't found solutions that contained digit 8 or 9

The description doesn't need to be updated because:
Ad. 1 Description says you have to "break a code of 3 digits" not numbers, and digits are integers;
Ad. 2 Digits are numbers but numbers aren't necessarily a digits, so they have their min/max value (look at the definition of digit)

This solution isn't a best practice because it can't find digit 9. E.g. for edge case of solution being [9, 9, 9], or any other solution where one of digits is 9, your tryCode function will not find a solution.