title: Error on Firefox Driver using Selenium/Python
body: <p>I'm getting an error when trying to execute a simple python script using Selenium. Here are the script and the error along with my environment information (I'm using a virtual environment). (I get a different error when I try to use the Chrome driver). Any help would be greatly appreciated. </p>
  
  <p>// SCRIPT //</p>
  
  <pre><code>import mechanize
  import urllib2 #requests web pages
  from selenium import webdriver
  from selenium.common.exceptions import NoSuchAttributeException
  from selenium.webdriver.common.keys import Keys #allows us to press keys
  
  import os
  import re #regular expressions module
  
  br = mechanize.Browser()
  br.set_handle_robots(False)
  br.set_handle_refresh(False)
  br.addheaders = [('User-agent','Firefox')]
  
  browser = webdriver.Firefox()
  browser.get("http://applebees.com")
  </code></pre>
  
  <p>//ERROR//</p>
  
  <pre><code>Traceback (most recent call last):
    File "scraper_test.py", line 18, in &lt;module&gt;
      browser = webdriver.Firefox()
    File "/Users/rachael/workspace/rbexplorations/email_scraping_challenge/venv/lib/python2.7/site-packages/selenium/webdriver/firefox/webdriver.py", line 77, in __init__
      self.binary, timeout),
    File "/Users/rachael/workspace/rbexplorations/email_scraping_challenge/venv/lib/python2.7/site-packages/selenium/webdriver/firefox/extension_connection.py", line 49, in __init__
      self.binary.launch_browser(self.profile)
    File "/Users/rachael/workspace/rbexplorations/email_scraping_challenge/venv/lib/python2.7/site-packages/selenium/webdriver/firefox/firefox_binary.py", line 67, in launch_browser
      self._start_from_profile_path(self.profile.path)
    File "/Users/rachael/workspace/rbexplorations/email_scraping_challenge/venv/lib/python2.7/site-packages/selenium/webdriver/firefox/firefox_binary.py", line 90, in _start_from_profile_path
      env=self._firefox_env)
    File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 710, in __init__
      errread, errwrite)
    File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 1335, in _execute_child
      raise child_exception
  OSError: [Errno 2] No such file or directory
  </code></pre>
  
  <p>// INFO ABOUT MY ENVIRONMENT //</p>
  
  <p>python 2.7.10
  mechanize (0.2.5)
  pip (7.1.2)
  selenium (2.48.0)
  setuptools (18.2)
  wheel (0.24.0)
  OSX 10.11.2</p>