systemctl: fix silent failure when --root is not found

Some calls to lookup_path_init() were not followed by any log emission.
E.g.:
$ SYSTEMD_LOG_LEVEL=debug systemctl --root=/missing enable unit; echo $?
1

Let's add a helper function and use it in various places.

$ SYSTEMD_LOG_LEVEL=debug build/systemctl --root=/missing enable unit; echo $?
Failed to initialize unit search paths for root directory /missing: No such file or directory
1
$ SYSTEMCTL_SKIP_SYSV=1 build/systemctl --root=/missing enable unit; echo $?
Failed to initialize unit search paths for root directory /missing: No such file or directory
Failed to enable: No such file or directory.
1

The repeated error in the second case is not very nice, but this is a niche
case and I don't think it's worth the trouble to trying to avoid it.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/sysv-generator/sysv-generator.c b/src/sysv-generator/sysv-generator.c
index a81df6600b..428509f4ce 100644
--- a/src/sysv-generator/sysv-generator.c
+++ b/src/sysv-generator/sysv-generator.c
@@ -891,9 +891,9 @@ static int run(const char *dest, const char *dest_early, const char *dest_late)
 
         assert_se(arg_dest = dest_late);
 
-        r = lookup_paths_init(&lp, UNIT_FILE_SYSTEM, LOOKUP_PATHS_EXCLUDE_GENERATED, NULL);
+        r = lookup_paths_init_or_warn(&lp, UNIT_FILE_SYSTEM, LOOKUP_PATHS_EXCLUDE_GENERATED, NULL);
         if (r < 0)
-                return log_error_errno(r, "Failed to find lookup paths: %m");
+                return r;
 
         all_services = hashmap_new(&string_hash_ops);
         if (!all_services)