core: WARNING: nonstandard use of escape in...

WARNING: nonstandard use of escape in a string literal

Adding use of the escape string syntax for escapes,

Change-Id: I168e1fe503c235d36b07aed18d88dc017726155e
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=958018
Signed-off-by: Eli Mesika <emesika@redhat.com>