def fill_package(app_name, build_dir=None, install_dir=None):
zip_path = os.path.join(install_dir, '<STR_LIT>' % app_name)<EOL>with zipfile.ZipFile(zip_path, '<STR_LIT:w>') as zip_file:<EOL><INDENT>fill_package_zip(zip_file, os.path.dirname(build_dir), prefix=app_name)<EOL><DEDENT>return zip_path<EOL>
Creates the theme package (.zip) from templates and optionally
assets installed in the ``build_dir``.