message: stack_decode.py: Adjust to work with Python < 3.7
  Specifically, the envoyproxy/envoy-build-ubuntu Docker image still has
  Python 3.5.
diff: @@ -80,7 +80,7 @@ if __name__ == "__main__":
  rununder = subprocess.Popen(sys.argv[1:],
  stdout=subprocess.PIPE,
  stderr=subprocess.STDOUT,
  - text=True)
  + universal_newlines=True)
  decode_stacktrace_log(sys.argv[1], rununder.stdout)
  rununder.wait()
  sys.exit(rununder.returncode) # Pass back test pass/fail result
  