Avoid "Selenium::WebDriver::Error::UnknownError" sometime on accessing log.

test/browser_test_helper.rb

@@ -3127,6 +3127,7 @@ wait untill text in selector disabppears
   end
 
   def log(method, params = {})
+    begin
       instance = params[:browser] || @browser
       if instance
         logs = instance.manage.logs.get(:browser)
@@ -3135,6 +3136,9 @@ wait untill text in selector disabppears
           puts "#{time}/#{log.level}: #{log.message}"
         }
       end
+    rescue
+      # faild to get logs
+    end
     return if !@@debug
     return if params[:mute_log]
     puts "#{Time.zone.now}/#{method}: #{params.inspect}"