Thanks very much for bringing this issue to our attention. The information that you provided is really helpful. As you pointed out, the vyprvpn cli installation is failing when executing the post-install script from our package. The contents of the post-install script are pretty straightforward: start vyprvpn.
I tried to reproduce this issue on a 15.04 vm but unfortunately was not able to - the package installed fine and the vyprvpn service was started without any problems. So I researched the error message that you provided. It looks like a few other third-party apps have experienced this same issue with their packages on 15.04. One of the bigger changes in 15.04 apparently is the change from using upstart to systemd. systemd is supposed to be backwards-compatible with upstart, meaning that the start vyprvpn command should have been able to start the vyprvpn service. However it appears that in certain cases these upstart commands are not being correctly handled.
Currently our vyprvpn cli package is only supported for 14.04, so for now, we're going to wait and see if this issue is corrected in a newer build of 15.04. If not, we'll have to put a workaround in our package, to start the vyprvpn service with an alternate command on 15.04.
Anyway thanks very much for letting us know, that's a great heads up for us, and sorry that you are having to use a workaround on 15.04.
Please let us know if you have any more questions or input.