L::Util: Make touch_file and open_gz exception-based

Change touch_file and open_gz so that they emit a trappable error
rather than returning on error.

Signed-off-by: Niels Thykier <niels@thykier.net>
Use q{} instead of "" for strings with a single quote in it

Signed-off-by: Niels Thykier <niels@thykier.net>