add DEFAULT_TBB_BROWSER_DIR

Author: milahu

tbselenium/tbdriver.py

@@ -21,13 +21,14 @@
 
 DEFAULT_BANNED_PORTS = "9050,9051,9150,9151"
 GECKO_DRIVER_EXE_PATH = shutil.which("geckodriver")
+DEFAULT_TBB_BROWSER_DIR = ""
 
 class TorBrowserDriver(FirefoxDriver):
     """
     Extend Firefox webdriver to automate Tor Browser.
     """
     def __init__(self,
-                 tbb_browser_dir="",
+                 tbb_browser_dir=DEFAULT_TBB_BROWSER_DIR,
                  tbb_path="",
                  tor_cfg=cm.USE_RUNNING_TOR,
                  tbb_fx_binary_path="",