temp_directory_path when temp dir does not exist

[dirkvdb]

When calling fs::temp_directory_path() on a clean windows machine that does not have a temp directory yet an exception is thrown with the message "not a directory".
This is because it checks if the path is a directory, but it does not exist so an error is created.

Is this the expected behavior because it is hard to recover from this error without calling native APIs to determine what the temp directory location is so it can be created.

[dirkvdb]

The path that does not exist seems to be present in the exception information so this makes recovery more trivial.