Build the absolute path of the to-be-saved thumbnail.

def build_thumb_path(self, image):
        """
        Build the absolute path of the to-be-saved thumbnail.
        """
        image_file = image.file
        image_name_w_ext = split(image.name)[-1]
        image_name, ext = splitext(image_name_w_ext)
        if not self.in_memory(image_file):
            # `image_file` is already in disk (not in memory).
            # `image_name` is the full path, not just the name
            image_name = image_name.split('/')[-1]
        upload_to = image.field.upload_to
        if not upload_to.endswith('/'):
            upload_to = f'{upload_to}/'
        path_upload_to = f'{upload_to}{image_name}'
        return f'{self.storage.location}/{path_upload_to}{THUMB_EXT}{ext}'