Add some more test cases for login

client/site_tests/login_BadAuthentication/login_BadAuthentication.py

Index: client/site_tests/login_BadAuthentication/login_BadAuthentication.py
diff --git a/client/site_tests/login_BadAuthentication/login_BadAuthentication.py b/client/site_tests/login_BadAuthentication/login_BadAuthentication.py
index 17e8b420ff28f6941572ea9b9d23194ae38968dd..401ef9231427b7e7fcc0f7c0439d8a4d3756b301 100644
--- a/client/site_tests/login_BadAuthentication/login_BadAuthentication.py
+++ b/client/site_tests/login_BadAuthentication/login_BadAuthentication.py
@@ -10,10 +10,12 @@ class login_BadAuthentication(site_ui_test.UITest):
 
     auto_login = False
 
+    _errorString = None
+
     def __login_denier(self, handler, url_args):
         handler.send_response(403)
         handler.end_headers()
-        handler.wfile.write('Error=BadAuthentication.')
+        handler.wfile.write(self._errorString)
 
 
     def start_authserver(self):
@@ -24,7 +26,8 @@ class login_BadAuthentication(site_ui_test.UITest):
         self.use_local_dns()
 
 
-    def run_once(self):
+    def run_once(self, error_string='BadAuthentication'):
+        self._errorString = "Error=" + error_string
         # TODO(cmasone): find better way to determine login has failed.
         try:
             self.login(self.username, self.password)