title: In python, selenium module . how to use firefox driver
body: <p>I want to use Selenium's Firefox driver.
  But I got the error shown below. Is it possible that Firefox didn't install properly?</p>
  
  <p>------ my source ------</p>
  
  <pre><code>from selenium import webdriver
  
  driver = webdriver.Firefox()
  </code></pre>
  
  <p>------ my source End------</p>
  
  <p>Here is the error that was returned:</p>
  
  <pre><code>Traceback (most recent call last):
    File "test.py", line 4, in &lt;module&gt;
      browser = webdriver.Firefox()
    File "/usr/local/lib/python2.7/site-packages/selenium-2.25.0-py2.7.egg/selenium/webdriver/firefox/webdriver.py", line 51, in __init__
      self.binary, timeout),
    File "/usr/local/lib/python2.7/site-packages/selenium-2.25.0-py2.7.egg/selenium/webdriver/firefox/extension_connection.py", line 47, in __init__
      self.binary.launch_browser(self.profile)
    File "/usr/local/lib/python2.7/site-packages/selenium-2.25.0-py2.7.egg/selenium/webdriver/firefox/firefox_binary.py", line 43, in launch_browser
      self._start_from_profile_path(self.profile.path)
    File "/usr/local/lib/python2.7/site-packages/selenium-2.25.0-py2.7.egg/selenium/webdriver/firefox/firefox_binary.py", line 65, in _start_from_profile_path
      env=self._firefox_env).communicate()
    File "/usr/local/lib/python2.7/subprocess.py", line 679, in __init__
      errread, errwrite)
    File "/usr/local/lib/python2.7/subprocess.py", line 1228, in _execute_child
      raise child_exception
  AttributeError: 'NoneType' object has no attribute 'rfind'
  </code></pre>