Estou executando um script python através de um cronjob. Eu tenho um ambiente virtual e no cronjob eu estou executando através deste ambiente virtual. Quando executo o script, normalmente o phantomJS inicia como deveria, mas executando-o através de um script em um cronjob, recebo esse erro. O que está faltando no cronjob para poder iniciar phantomjs?

Message: 'Unable to start phantomjs with ghostdriver.' ; Screenshot: available via screen
Traceback (most recent call last):
  File "/home/scraper/superfish-extension/chrome_3day.py", line 96, in <module>
    main()
  File "/home/scraper/superfish-extension/chrome_3day.py", line 73, in main
    browser = use_phantomjs()
  File "/home/scraper/superfish-extension/chrome.py", line 81, in use_phantomjs
    browser = webdriver.PhantomJS()
  File "/home/scraper/.virtualenvs/superfish/lib/python2.6/site-packages/selenium/webdriver/phantomjs/webdriver.py", line 50, in __init__
    self.service.start()
  File "/home/scraper/.virtualenvs/superfish/lib/python2.6/site-packages/selenium/webdriver/phantomjs/service.py", line 69, in start
    raise WebDriverException("Unable to start phantomjs with ghostdriver.", e)
WebDriverException: Message: 'Unable to start phantomjs with ghostdriver.' ; Screenshot: available via screen