Spark 6.0 installation issue on ubuntu 17.10

while installing Spark 6.0 + laravel 5.6 on ubuntu 17.10, it gets stuck at updating the dependencies. Here is the details :

Downloading Spark... Loading composer repositories with package information Updating dependencies (including require-dev)

Tried all methods of installation https://spark.laravel.com/docs/6.0/installation The Spark/Spark Aurelius GitHub Repositories are not accessible as well. 404 error!

any solution to proceed ?