StudyDesignForm does not get clean()'ed during validation.

[EdoStorm96]

For some mysterious reason StudyDesignForm's clean() does not get called during instantiation in get_form_errors(). Other forms do not have this issue. This form's full_clean() does get called during validation for some reason.

It is very unlikely that a user tries to submit with errors on this form (They would have to try to have a study with no intervention, no observation and no sessions), so it is not the end of the world in practice ... But it is very annoying.

Maybe this goes away when we switch to a new method of validation, but maybe not ...