Code review comment for lp:~parthm/bzr/300062-better-handling-for-invalid-ignore-pattern

> Why do they need to catch it? Why can't the exception __str__ just
> show it, avoiding all changes to add/ignore/ignored and status
> commands?
>
> -Rob

regex are used in other places like `log -m`. So, a failure
doesn't necessarily mean its an ignore pattern issue. Hence,
the caller needs to decide whats the best way to deal with
it. Also, in some cases we want to show a warning (ignore)
and in others, an error (add).