Returns the full path to the cache directory as specified in settings.

def _cache_directory(self):
        """Returns the full path to the cache directory as specified in settings.
        """
        if settings.unit_testing_mode or settings.use_test_cache:
            return os.path.join(settings.cache_directory.replace("Fortpy", "Fortpy_Testing"), self.py_tag)
        else:
            return os.path.join(settings.cache_directory, self.py_tag)