[Telemetry] Add comment to page_set_smoke_test. Noop change

tools/telemetry/telemetry/unittest_util/page_set_smoke_test.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import logging
 import os
 import unittest
 
 from telemetry.core import browser_credentials
 from telemetry.core import discover
@@ skipping 85 matching lines @@
         msg='page_set\'s archive_data_file path must have type string')
 
     if page_set.user_agent_type is not None:
       self.assertTrue(
           isinstance(page_set.user_agent_type, str),
           msg='page_set\'s user_agent_type must have type string')
 
   def CheckAttributesOfPageBasicAttributes(self, page):
     self.assertTrue(not hasattr(page, 'disabled'))
     self.assertTrue(
+       # We use basestring instead of str because page's url can be string of
+       # unicode.
        isinstance(page.url, basestring),
        msg='page %s \'s url must have type string' % page.display_name)
     self.assertTrue(
        isinstance(page.page_set, page_set_module.PageSet),
        msg='page %s \'s page_set must be an instance of '
        'telemetry.page.page_set.PageSet' % page.display_name)
     self.assertTrue(
        isinstance(page.name, str),
        msg='page %s \'s name field must have type string' % page.display_name)
     self.assertTrue(
@@ skipping 25 matching lines @@
       if not classes.IsDirectlyConstructable(page_set_class):
         # We can't test page sets that aren't directly constructable since we
         # don't know what arguments to put for the constructor.
         continue
       page_set = page_set_class()
       logging.info('Testing %s', page_set.file_path)
       self.CheckArchive(page_set)
       self.CheckCredentials(page_set)
       self.CheckAttributes(page_set)
       self.CheckNoMixedInBetweenLegacyRunMethodsAndRunPageInteractions(page_set)