It looks like the "mono-reference-assemblies-4.0" package is also required to build on Ubuntu 16.04 and above. I've updated the packaging for the PPA, so hopefully the next build will go through
It looks like the "mono-reference -assemblies- 4.0" package is also required to build on Ubuntu 16.04 and above. I've updated the packaging for the PPA, so hopefully the next build will go through