various: treat BUS_ERROR_NO_SUCH_UNIT the same as SD_BUS_ERROR_SERVICE_UNKNOWN

We return BUS_ERROR_NO_SUCH_UNIT a.k.a. org.freedesktop.systemd1.NoSuchUnit
in various places. In #16813:
Aug 22 06:14:48 core sudo[2769199]: pam_systemd_home(sudo:account): Failed to query user record: Unit dbus-org.freedesktop.home1.service not found.
Aug 22 06:14:48 core dbus-daemon[5311]: [system] Activation via systemd failed for unit 'dbus-org.freedesktop.home1.service': Unit dbus-org.freedesktop.home1.service not found.
Aug 22 06:14:48 core dbus-daemon[5311]: [system] Activating via systemd: service name='org.freedesktop.home1' unit='dbus-org.freedesktop.home1.service' requested by ':1.6564' (uid=0 pid=2769199 comm="sudo su ")

This particular error comes from bus_unit_validate_load_state() in pid1:
  case UNIT_NOT_FOUND:
       return sd_bus_error_setf(error, BUS_ERROR_NO_SUCH_UNIT, "Unit %s not found.", u->id);

It seems possible that we should return a different error, but it doesn't really
matter: if we change pid1 to return a different error, we still need to handle
BUS_ERROR_NO_SUCH_UNIT as in this patch to handle pid1 with current code.

src/home/pam_systemd_home.c

@@ -7,6 +7,7 @@
 
 #include "bus-common-errors.h"
 #include "bus-locator.h"
+#include "bus-util.h"
 #include "errno-util.h"
 #include "fd-util.h"
 #include "home-util.h"
@@ -153,8 +154,7 @@ static int acquire_user_record(
 
                 r = bus_call_method(bus, bus_home_mgr, "GetUserRecordByName", &error, &reply, "s", username);
                 if (r < 0) {
-                        if (sd_bus_error_has_name(&error, SD_BUS_ERROR_SERVICE_UNKNOWN) ||
-                            sd_bus_error_has_name(&error, SD_BUS_ERROR_NAME_HAS_NO_OWNER)) {
+                        if (bus_error_is_unknown_service(&error)) {
                                 pam_syslog(handle, LOG_DEBUG, "systemd-homed is not available: %s", bus_error_message(&error, r));
                                 goto user_unknown;
                         }

src/shared/bus-polkit.c

@@ -3,6 +3,7 @@
 #include "bus-internal.h"
 #include "bus-message.h"
 #include "bus-polkit.h"
+#include "bus-util.h"
 #include "strv.h"
 #include "user-util.h"
 
@@ -123,7 +124,7 @@ int bus_test_polkit(
                 r = sd_bus_call(call->bus, request, 0, ret_error, &reply);
                 if (r < 0) {
                         /* Treat no PK available as access denied */
-                        if (sd_bus_error_has_name(ret_error, SD_BUS_ERROR_SERVICE_UNKNOWN)) {
+                        if (bus_error_is_unknown_service(ret_error)) {
                                 sd_bus_error_free(ret_error);
                                 return -EACCES;
                         }
@@ -296,8 +297,7 @@ int bus_verify_polkit_async(
                         e = sd_bus_message_get_error(q->reply);
 
                         /* Treat no PK available as access denied */
-                        if (sd_bus_error_has_name(e, SD_BUS_ERROR_SERVICE_UNKNOWN) ||
-                            sd_bus_error_has_name(e, SD_BUS_ERROR_NAME_HAS_NO_OWNER))
+                        if (bus_error_is_unknown_service(e))
                                 return -EACCES;
 
                         /* Copy error from polkit reply */

src/shared/bus-util.c

@@ -14,14 +14,13 @@
 #include "sd-event.h"
 #include "sd-id128.h"
 
-/* #include "alloc-util.h" */
+#include "bus-common-errors.h"
 #include "bus-internal.h"
 #include "bus-label.h"
 #include "bus-util.h"
 #include "path-util.h"
 #include "socket-util.h"
 #include "stdio-util.h"
-/* #include "string-util.h" */
 
 static int name_owner_change_callback(sd_bus_message *m, void *userdata, sd_bus_error *ret_error) {
         sd_event *e = userdata;
@@ -153,6 +152,13 @@ int bus_name_has_owner(sd_bus *c, const char *name, sd_bus_error *error) {
         return has_owner;
 }
 
+bool bus_error_is_unknown_service(const sd_bus_error *error) {
+        return sd_bus_error_has_names(error,
+                                      SD_BUS_ERROR_SERVICE_UNKNOWN,
+                                      SD_BUS_ERROR_NAME_HAS_NO_OWNER,
+                                      BUS_ERROR_NO_SUCH_UNIT);
+}
+
 int bus_check_peercred(sd_bus *c) {
         struct ucred ucred;
         int fd, r;

src/shared/bus-util.h

@@ -28,6 +28,7 @@ typedef bool (*check_idle_t)(void *userdata);
 int bus_event_loop_with_idle(sd_event *e, sd_bus *bus, const char *name, usec_t timeout, check_idle_t check_idle, void *userdata);
 
 int bus_name_has_owner(sd_bus *c, const char *name, sd_bus_error *error);
+bool bus_error_is_unknown_service(const sd_bus_error *error);
 
 int bus_check_peercred(sd_bus *c);
 

src/sleep/sleep.c

@@ -160,11 +160,8 @@ static int lock_all_homes(void) {
 
         r = sd_bus_call(bus, m, DEFAULT_TIMEOUT_USEC, &error, NULL);
         if (r < 0) {
-                if (sd_bus_error_has_name(&error, SD_BUS_ERROR_SERVICE_UNKNOWN) ||
-                    sd_bus_error_has_name(&error, SD_BUS_ERROR_NAME_HAS_NO_OWNER)) {
-                        log_debug("systemd-homed is not running, skipping locking of home directories.");
-                        return 0;
-                }
+                if (bus_error_is_unknown_service(&error))
+                        return log_debug("systemd-homed is not running, skipping locking of home directories.");
 
                 return log_error_errno(r, "Failed to lock home directories: %s", bus_error_message(&error, r));
         }