complete-run: Use Carp::Always to get nice stacktraces in case of errors

testcases/complete-run.pl

@@ -13,6 +13,7 @@ use strict;
 use warnings;
 use v5.10;
 # the following are modules which ship with Perl (>= 5.10):
+use Carp::Always;
 use Cwd qw(abs_path);
 use File::Basename qw(basename);
 use File::Temp qw(tempfile tempdir);