Fix return type in `get_linux_type()` (#1025)
Fix return type in `get_linux_type()` (#1025)

Summary:
This function is expected to return a tuple of 3 elements. This doesn't happen when it fails opening the `/etc/os-release` file.

Pull Request resolved: https://github.com/facebook/watchman/pull/1025

Reviewed By: fanzeyi

Differential Revision: D36736667

Pulled By: chadaustin

fbshipit-source-id: a6839235d6c5ebb50267cd78f1c9590b2fb180d7

facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman