This is a fix for the UnauthorizedAccessException in Xamarin Studio (MonoDevelop) when running a MVC 4/5 website on Mac OSX.
The error:
System.UnauthorizedAccessException
Access to the path "/Library/Frameworks/Mono.framework/Versions/3.2.5/etc/mono/registry" is denied.
Description: HTTP 500.Error processing request.
Details: Non-web exception. Exception origin (name of application or object): mscorlib.
Exception stack trace: ...
Run the following commands to allow access:
sudo mkdir /Library/Frameworks/Mono.framework/Versions/3.2.5/etc/mono/registry
sudo chmod g+rwx /Library/Frameworks/Mono.framework/Versions/3.2.5/etc/mono/registry