Roll gsutil version to 4.15.

tools/telemetry/third_party/gsutilz/gslib/tests/test_Doption.py

Index: tools/telemetry/third_party/gsutilz/gslib/tests/test_Doption.py
diff --git a/tools/telemetry/third_party/gsutilz/gslib/tests/test_Doption.py b/tools/telemetry/third_party/gsutilz/gslib/tests/test_Doption.py
index ded088c70d62240de263a45a25010f80049af9e7..b5612a853abfb672307eb767314611c9ff917380 100644
--- a/tools/telemetry/third_party/gsutilz/gslib/tests/test_Doption.py
+++ b/tools/telemetry/third_party/gsutilz/gslib/tests/test_Doption.py
@@ -16,6 +16,8 @@
 
 from __future__ import absolute_import
 
+import platform
+
 import gslib
 from gslib.cs_api_map import ApiSelector
 import gslib.tests.testcase as testcase
@@ -88,8 +90,9 @@ class TestDOption(testcase.GsUtilIntegrationTestCase):
       self.assertIn('header: x-goog-hash: md5=eB5eJF1ptWaXm4bijSPyxw==', stderr)
     elif self.test_api == ApiSelector.JSON:
       self.assertRegexpMatches(
-          stderr, '.*GET.*b/%s/o/%s.*user-agent:.*gsutil/%s' %
-          (key_uri.bucket_name, key_uri.object_name, gslib.VERSION))
+          stderr, '.*GET.*b/%s/o/%s.*user-agent:.*gsutil/%s.Python/%s' %
+          (key_uri.bucket_name, key_uri.object_name, gslib.VERSION,
+           platform.python_version()))
       self.assertIn(('header: Cache-Control: no-cache, no-store, max-age=0, '
                      'must-revalidate'), stderr)
       self.assertIn("md5Hash: u'eB5eJF1ptWaXm4bijSPyxw=='", stderr)