'File storage returns a url even when its base_url is unset or modified.'

def test_base_url(self):

    self.storage.base_url = None
    with self.assertRaises(ValueError):
        self.storage.url('test.file')
    storage = self.storage_class(location=self.temp_dir, base_url='/no_ending_slash')
    self.assertEqual(storage.url('test.file'), ('%s%s' % (storage.base_url, 'test.file')))
