Metal Master

I found a potential easy solution! You see, I also had the same error, even one of the same libraries as you and @jarmyco were unable to install, and I found a relatively easy fix after about 2 hours of searching. If you, like me, are just trying to install forge to use forge mods with Minecraft, then this should work. For me, I was trying to install forge for 1.8.0. I had downloaded the Recommended forge version (not the latest version) for 1.8.0, but that version caused 1 or more libraries to fail to download/install. To fix this, I found that simply going back to the forge website and trying a different version of forge (still for 1.8.0) fixed it. For me, I tried using the latest version for 1.8.0, and it worked, but maybe you will have to try a few and find what works, I'm not sure how it all works tbh. It may just be a compatibility issue with certain versions of Java and certain versions of Forge. I had been using a very new Java version, and a very old Forge version. Good luck! - Metal Master