[infra] Fix syntax warning in the pub integration test

Change-Id: I40b91d3f24309d32c2b1201c675cdec9aed454da
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/198283
Reviewed-by: William Hesse <whesse@google.com>
Commit-Queue: William Hesse <whesse@google.com>
Auto-Submit: Alexander Thomas <athom@google.com>
diff --git a/tools/bots/pub_integration_test.py b/tools/bots/pub_integration_test.py
index 7264279..cef43cc 100755
--- a/tools/bots/pub_integration_test.py
+++ b/tools/bots/pub_integration_test.py
@@ -44,11 +44,11 @@
             pubspec_yaml.write(PUBSPEC)
 
         exit_code = subprocess.call([pub, 'get'], cwd=working_dir, env=env)
-        if exit_code is not 0:
+        if exit_code != 0:
             return exit_code
 
         exit_code = subprocess.call([pub, 'upgrade'], cwd=working_dir, env=env)
-        if exit_code is not 0:
+        if exit_code != 0:
             return exit_code
     finally:
         shutil.rmtree(working_dir)