I am taking a robotics course on EdX that requires us to have Ubuntu Wily (15.10) or Ubuntu Xenial (16.04 LTS) in order to use ROS (The Robot Operating System).
When I try to follow instructions to install the newer version (using the server version), I get the message
Package update-manager-core is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source E: Package 'update-manager-core' has no installation candidate
How can I upgrade the version of Ubuntu on Cloud9?