'Files are in the format of: {app_slug}-{version}.{extension}'

def generate_filename(self, extension=None):

    parts = []
    addon = self.version.addon
    extension = ((extension or '.zip') if addon.is_packaged else '.webapp')
    parts.append((slugify(addon.app_slug) or 'app'))
    parts.append(self.version.version)
    self.filename = ('-'.join(parts) + extension)
    return self.filename
