Error forwarding the new session cannot find : Capabilities [{browserName=htmlun

代码：

driver = webdriver.Remote(
                                          command_executor=' http://127.0.0.1:4444/wd/hub',
                                          desired_capabilities={'platform': 'ANY',
                                          'browserName': 'htmlunit',
                                          'version': '',
                                          'javascriptEnabled': True
                                         })

运行的时候报：selenium.common.exceptions.WebDriverException: Message:

Error forwarding the new session cannot find : Capabilities [{browserName=htmlunit, javascriptEnabled=true, version=, platform=ANY}]

当时有点迷惑，我把 'browserName': ''的value换成chrome.firefox,IE都没有问题，就这个htmlunit报错，查资料发现这个在启动selenium-server node的时候要指定一下

java -jar selenium-server-standalone-2.44.0.jar -role node -hub http://IP:4444/grid/register  -browser  browserName=htmlunit