docs: public NuProcess start()
     {
        if (processListener == null) {
           throw new IllegalArgumentException("NuProcessHandler not specified");
        }
  
        String[] env = new String[environment.size()];
        int i = 0;
        for (Entry<String, String> entrySet : environment.entrySet()) {
           env[i++] = entrySet.getKey() + "=" + entrySet.getValue();
        }
  
        return factory.createProcess(command, env, processListener, cwd);
     }