4220 beadm mount of old BE with zones fails "Read only filesystem"
4235 beadm(1M) mount options undocumented in man page

*** 1267,1276 ****
--- 1267,1280 ----
          case BE_ERR_ACCESS:
                  (void) fprintf(stderr, _("Unable to mount %s.\n"), obe_name);
                  (void) fprintf(stderr, _("You have insufficient privileges to "
                      "execute this command.\n"));
                  break;
+         case BE_ERR_NO_MOUNTED_ZONE:
+                 (void) fprintf(stderr, _("Mounted on '%s'.\nUnable to mount "
+                     "one of %s's zone BE's.\n"), mountpoint, obe_name);
+                 break;
          default:
                  (void) fprintf(stderr, _("Unable to mount %s.\n"), obe_name);
                  (void) fprintf(stderr, "%s\n", be_err_to_str(err));
          }