[Telemetry] Resolve errors due to new pylint checker.

tools/telemetry/telemetry/unittest_util/system_stub_unittest.py

 # Copyright 2013 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 os
 import unittest
 
 PERF_ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 from telemetry.unittest_util import system_stub
 
@@ skipping 67 matching lines @@
       self.cloud_storage.INTERNAL_BUCKET, 'preset_internal_file.wpr'))
 
   def testExistsNonEmptyCloudStorage(self):
     # Test non-empty remote files dictionary.
     self.cloud_storage.SetRemotePathsForTesting(self.remote_paths)
     self.assertTrue(self.cloud_storage.Exists(self.cloud_storage.PUBLIC_BUCKET,
                                               'preset_public_file.wpr'))
     self.assertTrue(self.cloud_storage.Exists(self.cloud_storage.PARTNER_BUCKET,
                                               'preset_partner_file.wpr'))
     self.assertTrue(self.cloud_storage.Exists(
-      self.cloud_storage.INTERNAL_BUCKET,'preset_internal_file.wpr'))
+      self.cloud_storage.INTERNAL_BUCKET, 'preset_internal_file.wpr'))
     self.assertFalse(self.cloud_storage.Exists(self.cloud_storage.PUBLIC_BUCKET,
                                                'fake_file'))
     self.assertFalse(self.cloud_storage.Exists(
-      self.cloud_storage.PARTNER_BUCKET,'fake_file'))
+      self.cloud_storage.PARTNER_BUCKET, 'fake_file'))
     self.assertFalse(self.cloud_storage.Exists(
       self.cloud_storage.INTERNAL_BUCKET, 'fake_file'))
     # Reset state.
     self.cloud_storage.SetRemotePathsForTesting()
 
   def testNonEmptyInsertAndExistsPublic(self):
     # Test non-empty remote files dictionary.
     self.cloud_storage.SetRemotePathsForTesting(self.remote_paths)
     self.assertFalse(self.cloud_storage.Exists(self.cloud_storage.PUBLIC_BUCKET,
                                                'success.wpr'))
@@ skipping 106 matching lines @@
       self.cloud_storage.INTERNAL_BUCKET)
     self.assertRaises(
       self.cloud_storage.CredentialsError, self.cloud_storage.Exists,
       self.cloud_storage.INTERNAL_BUCKET, 'preset_internal_file.wpr')
     self.assertRaises(
       self.cloud_storage.CredentialsError, self.cloud_storage.Insert,
       self.cloud_storage.INTERNAL_BUCKET, 'success.wpr',
       '/path/to/success.wpr')
     # Reset state.
     self.cloud_storage.SetRemotePathsForTesting()