if stderr is None:
    stderr = sys.stdout
  if allow_non_zero:
    try:
      output = subprocess.check_output(cmd, stderr=stderr)
    except subprocess.CalledProcessError as e:
      output = e.output
  else:
    output = subprocess.check_output(cmd, stderr=stderr)
  return output.decode('UTF-8').strip()


def cygpath(path):
  """Convert path from posix to windows."""

    Joiner onChar = Joiner.on('-');
    checkNoOutput(onChar, ITERABLE_);
    checkResult(onChar, ITERABLE_1, "1");
    checkResult(onChar, ITERABLE_12, "1-2");
    checkResult(onChar, ITERABLE_123, "1-2-3");
  }

  public void testSkipNulls() {
    Joiner skipNulls = J.skipNulls();
    checkNoOutput(skipNulls, ITERABLE_);
    checkNoOutput(skipNulls, ITERABLE_NULL);
    checkNoOutput(skipNulls, ITERABLE_NULL_NULL);