I'm trying to configure my Eclipse Luna on Ubuntu 16.04 to be able to use NS-3. I need to install a plugin called MercurialEclipse. The available download links (Bitbucket and javaforge) seem old and unnecessary. They display an error message saying:
Warning: you are installing software that contains unsigned content. The authenticity or validity of this software cannot be established. Do you want to continue with the installation?
The java version installed is JDK 1.8.0_191.