docs: @CheckReturnValue
      private boolean loadMasterKillSwitchFile(@Nonnull File f) {
          try {
              if (!f.exists())    return true;
              return Boolean.parseBoolean(FileUtils.readFileToString(f).trim());
          } catch (IOException e) {
              LOGGER.log(WARNING, "Failed to read "+f, e);
              return false;
          }
      }