'Verifies form for when no username is specified, including permissions.'

@staticmethod
def _verify_no_user(requesting_user, cleaned_data, course_key):

    if (not cleaned_data.get('all_blocks', None)):
        raise ValidationError({'username': ['This    field    is    required    unless    all_blocks    is    requested.']})
    if (not permissions.can_access_all_blocks(requesting_user, course_key)):
        raise PermissionDenied("'{requesting_username}'    does    not    have    permission    to    access    all    blocks    in    '{course_key}'.".format(requesting_username=requesting_user.username, course_key=unicode(course_key)))
    return None
