private static function get_core_checksums( $version, $locale ) {
		$query = http_build_query( compact( 'version', 'locale' ), null, '&' );
		$url   = "https://api.wordpress.org/core/checksums/1.0/?{$query}";

		$options = [ 'timeout' => 30 ];
		$headers = [ 'Accept' => 'application/json' ];

		$response = Utils\http_request( 'GET', $url, null, $headers, $options );

		if ( ! $response->success || 200 !== (int) $response->status_code ) {
			return "Checksum request '{$url}' failed (HTTP {$response->status_code}).";
		}

		$body = trim( $response->body );
		$body = json_decode( $body, true );

		if ( ! is_array( $body )
			|| ! isset( $body['checksums'] )
			|| ! is_array( $body['checksums'] ) ) {
			return "Checksums not available for WordPress {$version}/{$locale}.";
		}

		return $body['checksums'];
	}