An 'Import' of the file '{1}' was found in the project file '{0}'. This file is not registered as a safe file to import, ...

An 'Import' of the file '{1}' was found in the project file '{0}'. This file is not registered as a safe file to import, and could contain targets and tasks that are harmful.  If this imported file is indeed considered safe, then it can be registered by writing to the registry key {2}.