Whenever I try to construct a string based on **`self.live_server_url`**, I get python `TypeError` messages. For example, I've tried the following string constructions (form 1 & 2 below), but I experience the same `TypeError`. My desired string is the Live Server URL with `"/lists"` appended. NOTE: the actual test does succeed to create a server and I can manually access the server, and more specifically, I can manually access the exact URL that I'm trying to build programmatically (e.g. `'http://localhost:8081/lists`').

`TypeError`s occur with these string constructions.

```
# FORM 1
lists_live_server_url = '%s%s' % (self.live_server_url, '/lists')

# FORM 2
lists_live_server_url = '{0}{1}'.format(self.live_server_url, '/lists')

self.browser.get(lists_live_server_url)

```

There is no python error with this form (nothing appended to string), albeit my test fails (as I would expect since it isn't accessing `/lists`).

```
self.browser.get(self.live_server_url)

```

Here is the python error that I'm getting.

```
/usr/local/Cellar/python3/3.4.2_1/Frameworks/Python.framework/Versions/3.4/bin/python3.4 /Applications/PyCharm.app/Contents/helpers/pycharm/django_test_manage.py test functional_tests.lists_tests.LiveNewVisitorTest.test_can_start_a_list_and_retrieve_it_later /Users/myusername/PycharmProjects/mysite_proj
    Testing started at 11:55 AM ...
    Creating test database for alias 'default'...
    Traceback (most recent call last):
      File "/usr/local/Cellar/python3/3.4.2_1/Frameworks/Python.framework/Versions/3.4/lib/python3.4/wsgiref/handlers.py", line 137, in run
        self.result = application(self.environ, self.start_response)
      File "/usr/local/lib/python3.4/site-packages/django/test/testcases.py", line 1104, in __call__
        return super(FSFilesHandler, self).__call__(environ, start_response)
      File "/usr/local/lib/python3.4/site-packages/django/core/handlers/wsgi.py", line 189, in __call__
        response = self.get_response(request)
      File "/usr/local/lib/python3.4/site-packages/django/test/testcases.py", line 1087, in get_response
        return self.serve(request)
      File "/usr/local/lib/python3.4/site-packages/django/test/testcases.py", line 1099, in serve
        return serve(request, final_rel_path, document_root=self.get_base_dir())
      File "/usr/local/lib/python3.4/site-packages/django/views/static.py", line 54, in serve
        fullpath = os.path.join(document_root, newpath)
      File "/usr/local/Cellar/python3/3.4.2_1/Frameworks/Python.framework/Versions/3.4/lib/python3.4/posixpath.py", line 82, in join
        path += b
    TypeError: unsupported operand type(s) for +=: 'NoneType' and 'str'

```

Am I unknowingly attempting to modify the `live_server_url`, which is leading to these `TypeError`s? How could I programmatically build a string of `live_server_url + "/lists"`?

Here is the test that I am attempting...

```
from selenium import webdriver
from selenium.webdriver.common.keys import Keys
from django.test import LiveServerTestCase

class LiveNewVisitorTest(LiveServerTestCase):
    def setUp(self):
        self.browser = webdriver.Chrome()
        self.browser.implicitly_wait(3)

    def tearDown(self):
        self.browser.close()

    def test_can_start_a_list_and_retrieve_it_later(self):
        #self.browser.get('http://localhost:8000/lists')
        #self.browser.get('http://www.google.com')
        #lists_live_server_url = '%s%s' % (self.live_server_url, '/lists')
        #lists_live_server_url = '{0}{1}'.format(self.live_server_url, '/lists')
        lists_live_server_url = self.live_server_url
        self.browser.get(lists_live_server_url)

        self.assertIn('To-Do', self.browser.title)
        header_text = self.browser.find_element_by_tag_name('h1').text
        self.assertIn('To-Do', header_text)

```