We added a `.dir-locals.el` in commit: 9a77017d87
There's no need to have it per-file, with that people might think
to add other editors, which is the wrong direction.
Closes: #1206
Approved by: jlebon
The function returns a gboolean, replace g_return_if_fail with
g_return_val_if_fail.
Add similar checks to the other functions.
Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>