Allow exercises that generate errors

[sumedh10]

There will be situations where we want the solution code to generate an error. However, the exercise validator won't pass for these exercises.

Similar to R exercises, Python exercises should also be able to generate an error while still passing the validator.

Discussion

[filipsch]

@sumedh10 Can you give an indication of urgency, where this is needed, by what time this is needed, etc?

[sumedh10]

@filipsch Currently, there is only one exercise (the course will be launched in ~2-3 weeks) which could benefit from this feature and we could easily modify that exercise to not generate an error.

So, this is more of a good to have feature request.