The above error has just started occurring after our upgrade to Xamarin 4.
Here is the scenario:
We are using Visual Studio 2015 running in a Windows VM within Parallels on a MacBook Pro. The solution code is hosted on the Mac (not in Windows vm) and this is the crux of the problem.
As you will see in the attached file that contains the stack trace of the error, the exception thrown is a System.UnauthorizedAccessException accessing "/Mac".
If the code is hosted on Windows we don't get the error, but the point is that this used to work before the upgrade.
It looks like it's just a bug, but I thought you'd want to know (we can workaround for the time being), though if you know of a solution I'd appreciate it if you could let me know.